Hi Keith, Nice start. I was thinking about doing a road layout too as its squareish and not too colorful so I'll have to rethink now. I was considering as WWII type road block but we'll see.
Two tech things... First repeating stuff does help PNG but makes no difference to JPG and second, blurring helps JPG a lot but kills PNG. So a tip I would give is to pick one style of filetype and optimize for it but trying to do both may not work. My guess would be to go JPG and don't worry about the repeating blocks of texture.
Another small thing since I think this is your first challenge entry. I provide a link to a page of thumbnail entries so we can see the state of the nation in one glance and have quick links into those threads. Everyone gets an position on it but you have to tag successive new WIP piccies with a little script catching bit of text posted at the end just before you finish...
### Latest WIP ###
...the next image is your thumb ref. You will see them on many other posts (all the posts that have thumb images). Then if you post a new WIP it will get snagged and formatted the next time its ran.
Links to the thumbs page are also (and normally) posted on the initial challenge description thread too.