I just took the latest Avatar mod available and augmented it to have a greater selection capability. If you only use a handful of avatars, then don't bother. But if you want a large selection and the ability to filter that selection list, then this is a nice feature.
Features
Adding multiple groups of Avatars for better management.
Optional Formatting: White space – improving space management of Avatars on posts, and removal of line wrap
Optional Image Size ignore: Original Avatar code sets images to be specific sizes, until now. Allows for irregularly shaped images.
Vastly better management on Mass Edits.
Required: You must completely install and test successfully the Avatar Mod for 3.4 authored by Richard Kinser, and adapted by Hamlin from: www.ian-hamlin.co.uk/downloads/avatar34.zip or http://www.snitzbitz.com/mods/details.asp?Version=All&mid=52
I agree that the original Avatar mod is difficult to implement; there's a lot of detail. The forum where I've applied my mods has a lot of CSS already implemented which in turn makes it impractical to hand over the source.
I placed a copy of the Avatar version I used as a foundation for my mod on my website; this will guarantee that you'll have the same version to work from: