There is some really decent talent here, especially for their age.
On the 4 photo down, I was thinking "very abstracted birdseye view of coffee (or tea) in cups on saucers", but then the second photo from the same artist just made me think maybe they just like circles and are inspired by alien space symbols.
Arrow ARE unusual to see and it appears some are in a quiver. It is hard to discern what is behind the candle, although close up the leather colored bag shaped thing close up appears to be etched leather and the hair stick thing also looks leather. Viewing it that way, I still couldn't figure out what all was going on back there.
For the mortar and pedestal, I believe some artists that mix their own pigments sometimes use one of these for mixing pigments or getting the lumps out of the pigment powders before adding liquid. I don't mix my own, but I believe I have seen something about that several times along the way.
The one with the buildings by Baric, I had no idea, but for 2 seconds I googled Poseidon statues, thinking that might give a clue since there is one on the top of that fountain or gazebo thing. Little did I know how many places had statues of Poseidon, It was only a quick search and although there were many statues, I didn't immediately see anything that looked like that. Of course I could be wrong about who that is on top, but was guessing because of the trident in it's hand. Oh well...
It was fun to look through your photos.