Is Stack Overflow a good place to ask Photoshop questions, or is there another site in the Stack Exchange family for those questions?
Super User may be your best bet, but it depends a lot on what you're doing with Photoshop. I know that Stack Overflow and Server Fault are definitely not appropriate.
There are also graphic design (and photography) sites on Stack Exchange which may be a good fit.
Try Graphic Design on Stack Exchange.
If your question involves programming or automation, then it may be a good candidate for Stack Overflow. Have a look at the tagged questions for examples of what is appropriate.
After looking at those questions, if your question doesn't seem to fit in with them, then Super User would be the best place to ask your question.
Ask yourself: Is my question related to programming in any point?
If the answer is yes, then a good formulated question that fits the FAQ guidelines has its place on Stack Overflow.
I think it's possible to imagine a few automation questions about photoshop related to programming. But don't ask about non-programming stuff.
Photoshop itself is not programming.
You could also try the Photography site on Stack Exchange. If the questions are about processing photos, that is.
Otherwise, Super User is the place to go.