For your signature, go here:
Member Centre.
Second box from the bottom.
Your avatar is a whole lot harder.
There are many threads on this, so just check these links:
AVATAR: The Ultimate Help.
Get yourself an Avatar (picture by your name).
Updated Avatar Instructions.
handbook Guide.
The main guidelines for avatars are such:
GIF and JPEG file formats only with a maximum dimension of
160 pixels wide, by
320 pixels tall. File sizes are not to exceed
75k,
and animated GIF's are allowed. (physical size can extend up to 400 pixels tall for images under 50k in file size)
No profanity. No 3rd party advertising for any website(s).
No images that are similar to, or mimic any official ATS staff, FSME, reward, or other images used by ATS to designate special status without prior
permission from me, SkepticOverlord, or Springer.

[edit on 11/10/2007 by watch_the_rocks]