I mean sure if you don't mind the fact that ESLs tend to have horrible resolution. The chroma 74 you linked, for example, only displays 640x384 for a 7.4" panel. Good pick if they work for your application.
Depends on your viewing distance. If viewed from a few feet / a meter, that resolution is probably enough. The contrast ratio might be the bigger problem. From a low-effort search, photo paper has a contrast ratio of 100:1, while e-paper has a contrast ratio of only 12:1. Photos displayed on e-paper are going to look washed out.
thanks to lack of very rough pixel boundaries, eInk looks quite goods even at that res, actually. Photos looks perfectly fine, eg: http://dmitry.gr/images/chromaGrey.jpg
