A background pic needs to be very small.  If you do something with MGS, I would suggest making it tiny, and repeating the crap out of it.  A huge pic takes forever to D/L for the little 56k people.  Or you could have a huge silhouette 2 color embossed logo.  That wouldn\'t be too big since it wouldn\'t be too many colors.
To look for backgrounds, just do a yahoo search.  There are also tons of free buttons and animated gifs out there.