A few possible tags
- "history-of-psychology" This could be for questions about the historical development of the field. Update: I added this to your question history-of-psychology subject to there being no major objections by others.
- "philosophy-of-science" or "philosophy-of-psychology" for philosophical questions about psychology: e.g., the logic of empiricism, theory building, epistemology as it relates psychology, etc.
I would also like to have tags that relate to professionals working in psychology:
"teaching-psychology" for questions about teaching psychology at high school or university level (correction; we already now have the teaching teaching-of-psychology tag for this purpose)
We do have the publication-process tag for questions about publishing in psychology, selecting journals, peer review, issues around open access, citations, and so on
There are also a range of topics that relate to being a scientist or academic or phd student in psychology and the cognitive sciences. There is the site academia.stackexchange.com but I often find that the advice is general and that it would be good to be able to ask questions that were more psychology specific.
General idea for tags
In general, I think it's easier to justify the creation of a tag if:
You can point to at least three existing questions that would be better linked and well served by the creation of such a tag. That shows that (a) there is a need for the tag (b) that such questions are on topic for the site, and (c) makes it concrete how the tag might be useful.