They all look perfect to me except the fact that the
walls, floors and ceiling could bear some texture maybe.
Now they are very flat.
Or maybe you will use textures later, in this case the whole looks good.

The modeling looks great and realistic. Dont worry about textures just yet.

One thing that I noticed is that its too 'clean'. I mean. This is a garage, right? Give it a garage feel to it. Put some boxes rotated so they arent paralell to the walls, and pull them a little bit away from the wall.. make some piles of generic stuff (tools, newspapers, chains, etc).. Put some dents or general wear and tear on some of the lockers and things. make that tool chest so it has a drawer that doesnt look like its been closed in a long time. Some rags laying around woudlnt hurt, either.

When you get on to using textures, use gritty textures. put oil spots in or something.

Right now, your room doesnt look too realistic. like most of te stuff is up against the walls. Even if you put a mech in the middle, it will still just look like a big empty room with a mech in it. Imagine if you personally walked into a hanger like that. You woudlnt be too impressed. there isnt alot of character. You would also probably be thinking "Why is everything on those two walls?".

Populate the scene with traces of life. Make it look like humans have been in there before and worked in there.

I think a lot of grunge can be done with material maps (textures), but things also need to be off-kilter. Ceiling tiles need to hang down. A bench needs to be turned out from the wall by 8 degrees. Dangling bare light bulbs should provide the illumination.

And definitely put in that mech in the middle! (With a pool of oil beneath it, perhaps?)

u might wonna check out Rhino3D, its a CAD program, with which u can make the same scene in about 20 minutes