The arches are gone, sorry. We pay by the pixel, and something decorative that is that large was too expensive to be worthwhile. I love the arches also, but theyll be a staple of the first game rather than the sequel. I really do think these games are different enough that folks who really liked the original can still play that from time to time while probably still enjoying the sequel primarily. It's like Mario 1 vs Mario 3.
There may be some background objects you can climb on, not sure.
Yesterday I got the new lighting model working, which has important gameplay considerations as well as looking better, performing better, and adding support for colored light sources. Hoooooly heck does this look nice.