Hi all - I'm looking into this! There was a major new release for Xenforo (1.4) yesterday that I plan to upgrade to, hopefully next week.
For the avatar images, it's interesting. If you right-click and save-as, it downloads as a .JPG. However both of your avatar's aren't JPGs...one is a PNG and the other is a GIF. Renaming the extension and uploading them works:
The old VB had a habit of translating .png into .gif. I tend to use .png, the resolution and colors are more stable. I use .gif for B&W because it doesn't fuzz out the pixels, but its color management is atrocious, leaving it OK for Schematics.
When I get around to it I'll redraw my avatar to something new. Not sure what but closer to the new me.