ok, let's see if this works.

to put a background into your userlookup page, first, find a background you like. try http://www.eternitysilenced.com/neopets/collection/ for 900+. get the url for the background you like.

once you have the url, you need to enter it into the box under 'My Chat Profile' at the bottom of the main Chat page on neopets, along with the html code that makes it 'stick'.

the code is < body background = " enter your bg url here " >

take out all the spaces except for the one between 'body' and 'background'. in the line under the box, called Default neoHTML, write none. this should be it :)