Using one texture for large walls. It might work on walls with two layers (tilings) but with three or more it looks boring on flat walls.
Although they can add some fun I think it's a bit overdone in this map. Perhaps it's a matter of taste but I see lots of stacked crates scattered around a map as a cheap way of connecting things (pic2), just like most of the jumppads nowadays.It's not a big deal but when the only way of getting to an item (armor, health) requires some crazy jump (pic3) it somehow unbalances things since the player who can't do it is left with one armor.
Lift:- Some lifts like in q2dm1 or ztn-maps will only be activated when the player touches them. The advantage is you can drop down the shaft and use it as an extra escape route. (To stop a lift from going up too soon, just add a "spawnflags 1" key. You won't find that in the description of the func_plat but I think it's a nice trick.)
Also, the lift is now very bright (since the lighting is calculated with lift(s) in their end position). It might be nice to add one or two small lights in the shaft to make it less striking.
Stairs:- These stairs seem a bit cramped and pretty steep. Circular or 45 degreed stairs might look better here. (pic4). Just a thought.