Mixing resolutions is a bad thing unless you have a good reason to do it and do it stylishly. The forum banner for example, has successful mixed resolutions (the logo is 2x1 wide pixels mostly, the radial gradient is 1x1 pixels and the dither gradient is 4x4 pixels). Of course the bigger resolutions are faked, and are composed of zoomed up 1x1 pixels, but the effect on the eye is that of different resolutions on top of each other .
You did a lot of that, without any good reason, I'd say, on your former avatar. Looked stretched or resized at parts. I suggest you keep it 1x1 pixel maximum detail level at all times, for now.