A repeat of 24" is often mentioned - you can certainly make an OBW with smaller repeat, but you may get a smaller quilt. For example, if you have a 24" repeat, you can cut up to 6 x 4" strips to get your blocks. If your repeat is 18", you may only get 4 x 4" strips.
The big repeat gives lots of variety to the designs. I've been in classes where people had the same fabric, and even little differences in where the repeat is selected or the triangles are cut, makes completely different quilts.
Of the fabrics you have listed, my top pick would be the last one (Keepsake Calico Fabric- Floral Vine) - to my eye, the dark background makes the rest of the designs really pop. My next choice would be the (Legacy Studio Cotton Fabric-Hampton Court Fancy Leaf Green) - the paisleys and feathery leaves will give some really nice effects, or the (Tigris Master Floral) - I really like the clean lines and crisp colours - they would work up really nicely!
I've tended to steer clear of animal prints (altho I've seen some fabulous ones finished) just because cutting up the eyes bothers me. The fabric with the 'mountain lodge patch' - it would be very interesting to see what happens to the patches but I think I'd be disappointed.
Have you seen the folding mirror sets that can help you visualize what the repeats will look like? Can't use them for online shopping (hmmm - maybe you could if you printed out the swatch?) - Joanne's has these here:
http://www.joann.com/folding-magic-m...n/1076447.html.
I think it's hard to go wrong with OBW's - they have some sort of magic! In Maxine Rosenthal's OBW books, she has good tips for selecting OBW candidates, including having good contrast. If you don't have her book(s), your local quilting guild or library may have them. I'd really recommend finding a copy of one of her books - she really does a terrific job showing how to select, pin and cut the fabric effectively.
Good luck and have fun!