Hmm...some of the images, like for example the MLP userbars, are at least 3000x3000. I re-size them not at low as 150 or 50. The pixelated ones like my Pokemon userbar, I don't resize it too much. For example my signature, it has a Milotic pixel. It's a 64x64. I resize it to 50 or 60. If lower, it will look pixely.
Sorry for too much to read..