I think I have just found the best website in the internet for free game graphics, sounds and music:http://opengameart.org/
The OpenGameArt site has lots of game assets of all kinds, and all of them are licenced under some Free Licence, such as Creative Commons or GPL.
Most of those free licences place just one condition on you: that you credit the original author of the work, if you use the work in your own projects. So, it's all free to use, even in commercial projects, as long as you remember to credit the original authors.
Although some of those licences have a "Share Alike" condition ("GPL2", "GPL3" and "CC-BY-SA 3.0" ), which basically means that if you use the work in a computer game, then that game must be Open Source, just like the artwork is...which is a small problem for us, because our M484 Game Creation System is not Open Source. At least not yet. But I'm considering releasing it as such in the future, for many reasons...but I'll tell more about that later. :)
But anyways, lots of art and music at OGA is licenced in such a way that you can freely use it in your M484 game projects. Just pay attention to the many "Licence plates" there, and you'll be fine. :D
And if I eventually actually Open Source the M484GCS, then we could use 100% all of it without any worries. But we'll see about that.
Also, I have plans to make a "free graphics" section to this our website as well, which would have free ready-made graphics and tilesets, created both by Me and by You People...so most likely I'll soon join this whole "Creative Commons" craziness, because I find it quite addictive. :D
And in fact I already did, here is my OGA profile:http://opengameart.org/users/master484
I have uploaded some old stuff there that has been sitting on my hard drive for years, and will upload more in the future...this way all the graphics from my old abandoned projects will find some purpose; if I don't need it, then maybe someone else does, and so all the pixel art that I made didn't go to waste. :)