Odd, cause I show that graphic as being 1.6 KB. Are you sure you didn't add a few zeros to the size that you listed for that top image
The only problem I saw was that you cut your images at 1000 pixels. If someone views your forum at a greater resolution that 1024 x 768 then your background graphic will tile (an effect that may or may not look good).
I cut my graphics at 1560 pixels and my site looks good at 1600x1200.
Edit: I'd also make the background page color the same (or close to) the blue that you used for your wrapper. The dark blue on light blue is tough on the ol' peepers
