Given all the other excellent options out there that span the gamut from apps to hosted solutions (gallery2, jalbum, wordpress, redbubble, etc), I don't think there is a market at all for bespoke gallery development. As for commercial websites, again there are so many templates etc to choose from that practically anyone who can succeed in a semi-technical field like photography can successfully build a website. They vary in their quality but then so do commercial web developers.

I don't think specialising in "photographer websites" is a useful niche if you're a web developer.