Looking for tips to how to improve my map

[Leondias]

At the moment im doing a 4 player d&d campaign which have sent them deep into the underdark. through some really tough fights and searching for a particular object in the caverns in posession of the Drow they are soon entering what i would call the final segment of the adventure which will eventually culminate in a battle against a rather vicious opponent.

I have made the prototype of the map i want to use as an arena, and i would like some tips and suggestions in how i can improve my map.

This is the first map i have ever made so i hope i can get some good constructive criticism.

apart from changing the colors of the floor to something more fitting and putting in shadows i dont really know how i can properly expand on this map within what i can handle at the moment.

The floor tiles and altar i made myself and the pillars were supplied to me by my friend and i think they make it look quite good.

Looking forward to any help
-Leondias