As you discovered, PS's "wave" filter has some limitations. In the last few years, some of those limitations have been reduced, but probably, the easiest and most straightforward way to do this sort of thing in PS is to use either the "warp" or possibly PS's "puppet warp" tools:
http://creativepro.com/know-your-photoshop-distortion-tools/
Another very nice way is to use the use PS's "displacement" filter set to vertical, and base the displacement on a two or three very soft, out of focus vertical bars. I couldn't immediately lay my hands on a tutorial on this method, but it works very well and has the benefit that one can use it to apply the exact same warping on multiple images. The limitation on this method (in its most simple incarnation) is that verticals remain vertical and the result can look a bit funky if you need really large displacements.
Another way to do this, and probably the best, is not to do it in PS, but do it in Illustrator using its Envelope Distort function:
http://www.ehow.com/how_10074969_curve-images-illustrator.html
When Sam has a chance to see your file, he'll be able to suggest which is the most appropriate method in your case.
Tom M