Do not violate image rights
... and use correct attribution where required
Image rights are horribly complex - especially on the internet. The well discussed "Stop Online Piracy Act" (SOPA) makes "blindly" publishing images (e.g. from Google Image Search) on InfoBarrel more than risky: Even Lamar Smith himself, creator of SOPA, got caught infringing the law by not paying attribution to the image author of his private homepage's wallpaper. What's more, simply paying any attribution is not enough: it has to be done accurately, or it may still result in painfully high fines.
However, there is a quite simple solution to this problem without the risk of getting sued: find public domain images! Those may be used for any application - commercial or private, on websites or even offline. Read more about public domain here: Public Domain License
Finding public domain images
It doesn't get any easier than that
Growing rapidly, both in popularity and size, Pixabay.com has become the source for copyright free quality images. You can use any image from this site for commercial and private use without attribution to the original author. Use them online or offline - completely free. You can even download full size images without registration.
Some example images from Pixabay
But there is more to Pixabay
Besides stunning images, Pixabay offers a thriving community of photographers from all over the world. That's where all the photos and cliparts come from - voluntary users. Anyone can join and contribute to the project. Who doesn't have some great photos lying around on a hard drive, just waiting to become useful?
Clker for cliparts
On Pixabay you'll find both, great photos and cliparts. However, if you are looking for scalable SVG cliparts, then Clker.com is the best choice. There are tens of thousands of SVG files and they are all for free. It's not getting any simpler.
This is a work in progress with more resources to come ...