my comment on the screenshot from that map would be that

the textures all look too similar, you would find it hard to distinguish walls properly when in game, you cant have the surrounding wall as a matching building texture as it doesnt work it looks stupid to see a wall so high surrounding the map, also you have a hole in your map or did not include any lights as the lighting has no shadows or direction. It also means that your sky texture is incorrctly positioned as the wrong type of sky texture to have used

plus do you need so many crates all over the place? was there nothing else you could use as blockers? some of the proportions too look oversized particually some of the crates to wall thickness, if you look at the building on top of the building on the left, why would any structure only have three sides?

where you have manipulated walls into shapes (i.e the roofs of the buildings) you have stretched the textures so that they look incorrect,

Post some more screenshots if this is a bad example of the map