Like all parts of the design tool box - there's a time and a place for stock images. Given stock's low cost these days if you need some decent images but don't have the budget for a photographer - it's something to consider to add some character to a design. Here’s a breakdown of some of your options.

There’s two main types: Rights Managed & Royalty Free.

The following is a very quick breakdown of the difference. For a more detailed look check out http://www.stockphotography.com/faq/CompareGuide/NatureOfImagery.html

Royalty Free (RF) – Non exclusive, Cheap(er)

Royalty Free is basically you get a non-exclusive “free for all” license to use the image.  When you purchase the image you can use it in all different kinds of marketing. The down side is anyone else can purchase the same image as well. So you may notice the same image being used in several different places. Usually the stock websites show how many times something has been downloaded, so it’s not a bad idea to keep an eye out for those which are very popular. Basically it’s safe to assume the more expensive the RF the less chance you have of seeing it used in someone else’s work.

Rights Managed (RM) – Exclusive & Expensive

Right Managed basically means you rent the use of the image for a certain period of time, for a specific use. So these images are usually very good quality, but also are more expensive because you’re paying for exclusive use. So you could purchase the rights to be the only company to use an image in a marketing brochure, for one year, in North America. Exclusive doesn’t come cheap so it’s not practical when you’re on a tight budget.

The List of Stock Sites

A few quick notes:

• All costs in US Dollars. We also assume you’re buying the smallest number of credits you can (they usually expire after a year). So the prices here could be lower if you buy bulk credits.
• Web Quality = Around 800x600px
• Print Quality = Around  3500x2500 px (typically printable at 8.5” x 11” @ 300DPI)

iStockphoto (owned by Comstock)

$5-6 / image (Web quality)
$20-25 / image (Print Quality)

A long time favorite of mine, iStock was the first to market with user uploaded cheap stock photography, (well at least that I remember.) They were purchased by Comstock which is one of the long standing stock libraries which faced major financial problems because of companies like iStock. If you can’t beat them, buy them.

• Huge selection, generally medium quality images.
• Excellent search functions.
• Has a guarantee that the images are legally licensed. 

iStockphoto - “Vetta Collection”

$35-40 / image (Web quality)
$70-80 / image (Print Quality)

I-stock has a premium image collection called Vetta which as far as I can tell are higher quality RF images comparable to what you would find on Comstock, but for a lot less.

• Smaller selection, of excellent images.
• Excellent search functions.
• Has a guarantee that the images are legally licensed. 

DreamsTimeMedia

$2-3 / image (Web quality)
$6-10 / image (Print Quality)

Dreams Time Media came on the scene later then iStock but as far as I can tell never got themselves bought out. So their prices never crept up like iStock. They have a huge selection of images but are on average lower quality than iStock. Typically for a project with a tight budget I’ll use both istockphoto.com & dreamstimemedia.com in about equal measure.

• Big selection of medium-low grade images.
• Fairly good search tools.
• Cheap.

Stock.xchng

$0/image !!! (read the warning below)

The Stock Xchng is actually free – for real. There’s lots of images, many are garbage but a few are really good. Like all to-good-to-be-true deals there’s a problem. If you read their licensing they waive all claims to the fact that the person uploading the image actually owns it. So imagine you use one of these great free photos, but it turns out that someone stole the image off of google and uploaded it onto Stock.xchng – You’re liable for any infringement of copyright held by the real image owner. It's a risk you take when using any images from this site, and I’d bet any lawyer would advise against it.

• Free!
• Basic Search.
• You may get sued for copyright infringement!

gettyimages / jupiterimages

(Royalty Free Prices)

$150 / image (Web quality)
$450 / image (Print Quality)

These are two companies that I’ll lump into one entry because they're not really “on a budget” sources. They offer a excellent library of artistic and conceptual images. I would recommend spending the money on a great shot for a homepage or cover, and if you can’t find what you need from one of the cheaper sites then buy one “money” shot. Ultimately your budget will determine if this is possible.

• Great Images.
• Great Search Tools.
• Expensive!

The fall of the "Big" stock agencies came at the hands of cheap digital cameras.

A few years ago stock images cost quite a bit more and was supplied by a few agencies who staffed photographers to produce their catalogues. You got printed books of images and ordered the images you needed for a specific use in a specific piece. But in the last 5 years most of those companies have drastically downsized or gone out of business because of the proliferation of "upload your own" stock photography websites. The main surviving players in the stock photography house tend to be very specialized in say celebrity images, or industry specific images.

So what used to cost $500/image and was limited to use in a specific ad or publication now costs $20 an can be used in anything you like.

$500 vs. $20 for an image... What's the difference?

Well first off as anyone with a camera and an internet connection can now post their images to a stock website it’s clear that the quality of work posted has decreased. As many, many agencies use cheap stock sources - out in the wild the overall quality of images has definitely decreased in quality over the past 10 years. This means that you should expect to sift though lots of garbage to find the needle in the haystack. Thankfully the search tools that the stock sites now use are great for hunting through hundreds of images quickly. But as a general rule of thumb you get 2 things by paying more for your images: Better, more interesting photos, and less of chance someone uses the same image you do.

One last Suggestion – Use the light box feature when looking through the haystack.

I've found what starts as a quick search sometimes becomes a marathon. Nothing is more frustrating after a long session then realizing the first few images you found hours ago are better then what you're looking at now. Remembering exact keywords you used to find those images is at best a waste of time. It's easy to avoid this issue by saving the images to a "light box" as you find them.

So before you start your search:

• Create an account with the stock website.
• Create a light box for your project.
• Set the number of thumbnail images per page view to the highest number possible (40-100 images)
• Open each image in a new tab (Middle button in most browsers).
• Close the tabs you don't like, and add your selections to the light box as you find them.

Please always read the fine print on any website you buy images from. Good luck and happy hunting! If I’ve missed any good photo resources please post a comment and I’ll add it the article.