Feedback time.
I took the liberty to run around the map and took some screenshots along the way.
First of all, it looks like you forgot to pack any custom material/model into the bsp, so any model or material that shows up fine for you is actually displaying either as an error sign or a purple/black checkerboard texture on our end since we don't have the models and/or materials. You can see that in the image below.
Now that that's out of the way, lets go over gameplay.
First the spawn. Coming out of the respawn room I'm faced with this wall. Usually with this kind of spawn room design with the two exits facing each other there's a window here to the outside world that can only be viewed out of from the inside. Look at Thunder Mountain's first BLU spawn, or Cactus Canyon for example. This is so players see where their objective is. Another thing that would help is arrows. You can never have enough of them.
Then there's this. The carts are up there yet there's no way up there other than to walk all the way around the giant wall in the middle. Even something as simple as a staircase would help massively in this case. And actually I would suggest a building over the middle and lower ground to the spawn (not a spawn exit), something like Badwater's drop under the building between 2nd and 3d point) to walk into. It gives more hight variation.
This Sniper balcony gives the Sniper a view over basically the entire map. Don't do that. A Sniper should not see the entirety of the map from one point.
The finale on both sides is a room with just one entrance/exit meaning a group of Engineers can sit in here Rancho Relaxo-ing all day while their sentry guns do the work meaning the round may very well never end. A room should just about always have at least 2 ways in and out of it. Try playing with the area just above the finale (where the carts initially are) with a connector of some sort.
This area has a thing I like and a thing that's generally not a good thing. The thing I like are the vents. Just a nice way around. The thing that isn't good is the health/ammo placement, which is just one each on each side. This means that one team gets access to a full health pack faster while another gets ammo faster, which is a pretty big imbalance (I'd take health over ammo any day) If you have a symmetrical map you should also make the health/ammo placement symmetrical.
I like the spawn room detailing! I do feel though that that steel bit that sticks out is a bit random. See what you can do with it, detailing wise.
Try to avoid sudden texture shifts from brush to brush. It looks weird and unnatural. Usually this seam is covered up with a support beam or something similar.
Don't put the bombs so close to each other at the start. It makes for a very narrow and spam heavy room with just 1 way out for each team. Instead, look at how a map like Hightower has the bombs separated (although Hightower is considered a pretty DM-only map Snowramp's layout is very similar to Hightower so that's why I'm comparing them to each other).
Again, a Sniper can snipe from his spawn to the other spawn. The wall in the middle kinda helps, but not enough. I suggest making a building in the middle instead of that wall where the carts also run trough with some upper areas, again, to have more hight variation and block this sight line.
This is where I'd put that building I mentioned above.
Visible nodraw in BLU's spawn. RED's spawn doesn't have this.
Rotate the texture on that wooden beam by 90 degrees so it actually looks like a beam.
It's almost impossible to notice that this is an off-limits area due to the chickenwire basically becoming invisible at range. Use more different materials or detailing to make clear that this is not accessible.
This bit of wooden floor at the bottom feels random. I'd make it all ground. Also, us mappers generally use two different overlays for both health and ammo instead of just one.
Finally, we come to this drop down. If you walk from the top end to finale you're guaranteed to take fall damage, even without jumping. This is usually a sign of overscaling which means things are too high up. Either make the bottom bit of the map go up or the top bit go down.
End of feedback.