Some background design advice please

[Nionicle]

This is for a personal portfolio/experiment site.

I want to do a back ground that works the same way as
www.webagent007.com

I designed a few examples but I noticed quickly that the .jpg size went really high with diagonal scan lines but other repetitive backgrounds still stayed noticeably smaller size. Why is that?

For a centered content area, what is a fairly good size? I was doing 800px but I started thinking that some people may still be in the dark ages. Is that too big for that sort of back ground style?
I was thinking of 600px would be ok... What is your oppinions.


I realize I may need to elaborate more. Just tell me where and what.
Thanks in advance =)

Mike

[Jujumon]

Im not sure which backgrounds that you're comparing them with. But i dont think scanlines would have anything to do with increase the jpg file size much (have u check .jpg optimization??)

Also, i guess you can actually create it with flash vector graphics, that perhaps may keep the size down.

i tend to work with somewhere between 800-1000px. not 600, just me though

-juju