I did a quick search on kbin and the Lemmy community browser and didn't see any dedicated photo critique spaces... yet! Of course you're welcome to post anything analog in /m/darkroom for feedback.
If you feel like you're up for committing a bit of time to moderating and growing a new space, creating a magazine is really easy—just mouse over the plus sign in the upper right, and click "Create New Magazine". You'll fill out a few details and you're all set. After creating mine, I filled out the sidebar with some basic info and created a sticky welcome thread so that the main page isn't blank until you get a few users. Then I posted in some related magazines on kbin and elsewhere trying to spread the word without being too obnoxious. I also made posts in /r/darkroom and /r/analog on Reddit. The good news is that my advertisements here were well received—it seems like everyone else is just as excited to see a new magazine getting started. Take a look at my profile if you need some examples, and feel free to post here if you decide to go this route and need some more help.