The possibilities with the existing set of faces run pretty deep when you consider how much you can customize the colors and complications... especially if you use apps that let you customize the complications they offer. I think it's a good mix of high information faces (ones with multiple complications) low information faces that are beautiful to look at, and few that are just cool to play with. Yes there could always be more (and I'm sure they will add more motion and Timelapse faces), but how many do you really need? Until recently just about every watch sold on the planet offered only the face you bought it with.
I find that I mostly rotate between just a few faces anyway. For a long time Utility and Modular were my favorites for times during the day when I need to be productive and stay informed. Currently i'm really liking the Color face with complications for weather, calendar, tasks and activity rings. Other times, like when I get home and don't need so much information, I will switch to a more relaxing watch face (Photo Album, single photo), or to a fun one like Motion, Astronomy or Solar. For the photo faces it really helps to select and crop photos that will look good on the watch. I totally agree with the decision to not put complications on the faces that are designed to show off photos or motion. That said it would never hurt to have the option. I could see complications working fine with certain photos.
I am sure that there will one day be a way to get even more watch faces, but for me it's really not something I ever think about. If i had more options I would probably still stick with the ones I already use the most: Color, Utility, Modular, Photo/Photo Album and Motion.
Sean