Not bad for your first map. Not sure if you plan on updating this at all, but here's some feedback:
- Try to use a larger grid (like 32x32) more for things like the stone block walls to ensure the textures are aligned.
- Lots of textures are misaligned in general. Not going to point them all out, but the barrels probably stand out the most.
- There's a metal texture just like the on you used that has a HR4 version. Originals had basically 2 of the same texture, and one wasn't really used, so I didn't make a HR4 version of it (yet). Might want to use the other one.
- Railings are super thick -- this is one case where you'd want to use a smaller grid.
- Not a huge fan of the layout overall. Lots of paths require trick jumps. Second flag is right next to the first and seems to only exist to make it easier for trick jumpers to get more points over newbies. Lots of little thin ledges and subtle paths. I'd suggest making the paths clearer and more accessible to new players.