This depends on whether you want vector graphics or raster graphics for 2D, or you're after 3D. For raster (pixilated) graphics, GIMP is a very decent program for that. I don't know of any programs that make vector graphics.
For 3D, this is also an unknown to me. I'm leaning mostly toward either GameStudio (not free) or TrueSpace (never seen though I've heard it's free). Blender is a last resort, but it's confusing to use.
Hello,
i need more computer graphic software than please send me direct link or any website which makes it easy to me.
I really like Pixlr editor
http://pixlr.com/editor/
It's completely online so there is nothing to download and the editing capabilities are quite good. It has layers, levels, and all sorts of other Photoshop-like functions.