Adding a frame to a square picture or other cropped image can make a great difference to how your avatar appears.
Adding a simple one pixel border can make the picture stand out much more.
Experiment with different colors. Make the border match the color set of the picture or try and blend or contrast with the forum.
With this set of images you can a small difference. There's a slight transition between the forum and the image. With the light blue color of the forum a darker or more contrasting color might have been more suitable.
This technique is a personal favorite of mine. This picture actually has a three pixel border. For this style you pick two colors(making sure the look good) and sequence them in order of color(x)-color(y)-color(x). This style of border can really make your image pop.
You may have noticed something odd about all the bordered images. The colors are smudgy and there is artifacting.
MS PAINT combined with the JPG file type are your enemies.Together, they both do a stuff job of encoding the image in an effort to make it take up less space.
Please use an alternate file type like PNG and a program like Adobe Photoshop or Paint.NET. Saving as a JPG is an option with a higher quality photo-editor.
If you choose to use JPG avoid resaving as much as possible. Every time you save that JPG it will lose quality. Another reason the bordered images have artifacts.
etc.
