Most avatars seem to be resized imaages or animated gifs. In my case, I take the easy and quick approach of taking a screenshot from my LCARS system and just clipping out a rectangle of the required size with MS-Paint and saving it as a png file, since png is well suited for LCARS clips. In that unusual scenario, no resizing is necessary.
If it were a photo, I'd probably make it jpeg but not use MS-Paint, since there are many programs that convert a bmp file to jpeg of better quality. Still gif is okay, too, but gives you lower color depth.
Here's another example of clipping a detail rather than resizing:
If it were a photo, I'd probably make it jpeg but not use MS-Paint, since there are many programs that convert a bmp file to jpeg of better quality. Still gif is okay, too, but gives you lower color depth.
Here's another example of clipping a detail rather than resizing:

(As a graphic designer it really hurts to hear that! Try to get Photoshop. Or CorelDraw if you must. But never ever use Paint. This program has nothing to do with graphic editing.)
And if you're searching for an avatar again, I'd like to help you. Just say what you want. Ach bin ich heute wieder nett. 
