[WIP] My first mapping attempt - small cave lair

[Pineapple]

Hi everyone, this is my first crack at a dungeon map. (Or any map, actually.)

It's being created in GIMP following the great tutorial by Jonathan Roberts at NewbieDM.

It's going to be the final encounters of a 1st-level adventure. After tracking some kind of cave-dwelling creature (I'm thinking kobolds) back to their lair, the party will finish them off.

So here's the map as it stands right now:


I'm still juggling ideas for the northernmost room. It could be a makeshift prison, or a dumping ground for caravan goods the kobolds have stolen that are not as interesting to them. I also considered the idea of it being the territory of some other cave monster the kobolds either avoid, or feed their prisoners to so that it doesn't get hungry enough to attack them.

The two main encounters with the kobolds themselves will happen in the two medium-sized rooms with pools of water.

I know it's small, but that's intentional. We only have a couple hours to play on Sunday nights and this will be for our first attempt at using a virtual tabletop over the internet, so I want to keep it simple and let everyone get a feel for the interface. (And there are a couple players who are either new to D&D or rusty.)

Plans for finishing it:
1) I'm actually realizing as I'm looking over it to post it that it's going to have to get larger, at least in one or two places. The rooms are just too small for a full party to maneuver in against multiple NPCs. I might accomplish that just by shrinking the grid (currently 100px).
2) Naturally I'll eventually have to add a few touches to make it look like a place sentient creatures have been using (some simple bedrolls or the like) but I don't want it to get too busy.
3) I'm not crazy about the parchment texture look for cave floor. I'd really like to try to get the floor to look like naturally water-smoothed cave rock, so any input on how to do that would be very much appreciated. I'm fine with the walls, the tutorial's approach leaves a nice, neutral, non-distracting wall.
4) I'd like to make the cave floor right in front of the pools have a glossy sheen without losing the appearance of rock, as though it's wet and slippery - and any character that finds him or herself fighting or running too close to the water has a chance of slipping. I would love pointers on that as well, if anyone has any.
5) There's supposed to be an underwater tunnel connecting the two easternmost rooms that have a wall between them. What I would like, though, is for the PCs to have to go looking for it. When they first enter the room in the virtual tabletop, fog of war will hide the small room at the other end of the water tunnel. Adventurers brave enough to try to poke around underwater will find the tunnel, and the side room will contain some extra treasure the kobolds had hidden away. I'm trying to decide whether to have the suggestion of a hole/tunnel at the bottom of the cave pool faintly visible, or to simply leave the search up to game mechanics.
6) I haven't had a chance to put in shadows, but I was waiting until I figured out whether I had a way of doing a more cave-like floor texture first.

I hope that wasn't too much explanatory text. I would welcome any feedback, tips, ideas, etc. Thanks!

Edit:
Here's tonight's progress, which includes a smaller grid, some shadows, cave textures and blended borders between water and stone.