Hey

It's cool that you're giving mapping a go! I'll go ahead and give you some pointers on what I feel could be improved.
The first thing that struck me is the size of your building. It's enormous! If you can't think of ways to make use of the interior space, chance are scaling it down a notch is the better option. In this particular case, I'd probably cut off between 2 and 4 SQM both horizontally and vertically. Furthermore, the colour scheme is a tad too simplistic; there's a whole lot of gray colour, but really nothing to contrast it. As it is now, the main thing drawing attention in the screenshot is your tiled floor, and the floor being the center of attention is seldom a good thing. The main focus should lie at the more important parts of the screenshot. In this case, that would be the depot lockers, the teleports, the staircase and also the entrance(s) to the building. Speaking of entrances, your southern one is
very wide. There's not really any need for an entrance of that width, and I'd recommend you to also scale that down.
To sum it up, here are the general ideas you should keep in mind for the next revamp/new piece:
Always keep purpose in mind. (Doesn't have to be functional. For instance, beautiful scenery also serves a purpose)
Be wary of colour combinations and how these will determine what areas of your map will stick out most to players.
Try not to make things
too big.