The textures, I already believe you know needs a lot more work. I assume these are just quickly made just to not make the map look too plain. And of course more weapons but I also think you know this as you just put in some just for us to play with. Same story with small health/armor.
Now to the meat of it. The gameplay looks like it could work quite well. Won't know until I try with someone but initially it looks promising. Maybe making it a little bit bigger or re-arrange some rooms. It feels like you can spam mortar in pretty much every direction and be able to hit your opponent as long as you approximately know where he is. But again, this is why I need to try it out with someone.
Lava problem 1: Aside from what machine already mentioned there is another problem. If you fall into the lava where the mega armor is you just lose little health as you fall in. But you didn't extend it to the bottom so you can actually swim under the lava (and on the surface) without losing health. Also you're unable to get out of it if you try to swim to the floor (maybe that was something you meant to do). You basically have to laser yourself up if you want to get out. Check that area out.
Lava (and culling problem) problem 2: Just below the 50 armor in the lava. You only lose health as soon as you enter it, not continually losing health like you should. So you can stand and bathe there without a problem. You can also see beneath the lava a little. Culling problem.
Culling problem 1: While speaking of the 50 armor. Just the opposite side it in the little corridor, hard to explain so I'll show pic.
Culling problem 2: There's a culling problem where the machingun is. Underneath the boxes, the whole length of the platform, you can see up too the jumppad if you walk close enough.
Culling problem 3: Above the shotgun shells, rectangular/square shape going into a beveled area.
Culling problem 4: Where the 50 armor is, underneath the stairs.
Culling problem 5: The grid on the ceiling in the corridor to the mega armor. One side is not textured (the other side is).
Z-fighting problem: On the lower level on your way to the mega armor. Below the little "widow" the textures are fighting with each other. Be a nice soul and break their fight up.
Lastly the area where the mega armor is could do with some renovations (the the area where the jumppad for the 50 armor is too), it's looks a bit too squary and plain. Not sure how much I like those sharp corners where the mortar is.
ai am ai.
Fix the avatar size limit please! I want my avatar gifs back! DISCRIMINATION!
Also, change my name to 'ai', these forums sucks which can't have 2 letters in the nick!