I've developed some kind of opening "system" that I like to play as black that takes a pretty closed approach. I like it because it can be played against pretty much anything (I think). I'm sure there's a name for this kind of thing or something similar but I can't find much and I am having a few problems. For example I am never sure whether to castle or not and on which side (queenside always tends to open up and I don't keep many pieces for defense on the kingside). Also I tend to get into a "stuck" position after a point where my pieces are safe and developed and I'm not sure what to do next. Anyone have some tips? Here are some examples of positions I get into (depending on what the opponent plays) Are there any weaknesses I could fall into with this?

Not much to say. You're playing into something that is pretty much the French or the Queen's gambit declined, depending on what white does! The placement of the pieces is not obvious, after all there can never be so many pieces out if white can advance the e5 pawn. In the first diagram it is not obvious why you even moved the queen. Then in the second diagram your kingside has no cover from the f6 knight and you weakened the light squares pretty badly by playing a5. White would simply play Nc3-b5 and score the bishop's pair I think.

I showed you some complications above.