A very important point. The existence of a category must come about from a need for one - only if the item being posted really does not belong anywhere else. Some forums go head over heels with categories and sub-categories, but that really doesn’t do much good, and becomes difficult to clean up as time passes.
I agree that Showcase and Critique are two different things, but is the distinction between the two clear to all and will it be obeyed? Not everyone who speaks English well will take the moment to think about which one to post in, and not everyone here speaks English well enough to understand the implications of the not-too-clear difference in category names. Furthermore, I feel that showing photos here while implicitly (by the name of the category) being forbidden from constructive critique goes a little against the spirit of the site.
Back to the main question.
“DIY Photography” and “Hack” greatly overlap, while “tips and tricks” is too general.
I suggest instead adding a category “Hardware”. It will combine several suggested categories and fill in a gap. It’s very clear what belongs there - DIY, hacks, gear talk, etc.
“Articles and useful links” again is too general - we already link to articles in the appropriate categories which the articles belong to. I don’t think there is a need for an Articles category, it wouldn’t improve anything.
I’m unsure what to do with threads about image processing scripts. They will get lost in the Software category. For example I posted a Bash script some time ago in Software, Easily generate DCP profiles using DCamProf and this Bash script. The only way to find it is to search for it. Maybe Software could use a Scripts sub-category? There are already a bunch of them floating about. Or maybe I should move that to github? @patdavid?
Then there is the question of buying and selling stuff, e.g. second-hand lenses, or some DIY electronics. “Buy & Sell” could be a sub-category of “Hardware”.