Not too bad, but there are some things I would advise.
Some things are a bit too boxy, and/or undetailed, such as that box room thing in the first picture, and the overall room in the third picture is just a big rectange.
The crate spam is ok I guess, but the brick spam is too much IMO. There are just so many it makes it feel cheesy. I know it might be more realistic to have a lot, but that many little squares just isn't good looking. Unless you're aiming for cheesy, I would advise toning down the number.
The third picture looks like the start of something that could be good, but you will need to work more to get it looking professional. That wall texture is not particularly appealing, and there is a horrid lack of details. Four giant walls with one texture will never look good, but adding details to the walls will really help. Also, I'm really not a fan of either of the orange textures for the pipes in the third picture, (although it works alright in the second one) but that is some personal opinion. I would also think about changing the size/detail of the main pipe/reactor/w.e it is in the bottom of the third pic, as it looks to big, and the textures are a bit stretched. Lastly, I would advise adding grating or something over the bottom, as I've never found a time when that texture you have for the floor works alright when uncovered over a huge surface.
Last point right now.... Lighting. The artistic qualities of lighting is something which is think is not used or understood enough by many mappers. The lighting in the third picture is alright, if uninspired, but I think you will have to wait until you change up that room to fix the lighting. In the first and second pictures, you have almost opposite problems. In the first picture, your lighting is very stale and monotonous, resulting in a washed out look, most likely because aside from that one pinkish light I see, all your lighting comes from that skybox. Skybox lighting is not bad... but try adjusting it so that you have different values and intensities, or dim it down, and add inside light sources. In the second picture... I have to say it could be good but your lighting needs fixing for sure. In some places you have pitch darkness, so you have lost 100% detail in the photo, it's just pure black. Pure blackness is not good for maps, very very dark, is good, but not pure black. Of course, pictures are different in some ways from in game, but no detail is no fun for anybody. On the other side of the spectrum, (see the "light pun"? oh my god, there's another one, I'm feeling really bright) you have some parts that look washed out from the lighting. There are quite a few things wrong with this. 1.) The pink/red lighting is clashing horribly with the grey cement texture, resulting in a sickly pinkish-almost yellow color, which I think of as quite undesirable, 2.) the bright lighting is highliting your stretched textures, which aren't looking so good. ((That's another thing, shrink down some of those textures, this is a typical newb mistake, being too lazy or not knowing how to get better results, or something, but I see a lot of stretched out textures in many newb maps from not being fit properly)) and 3.) The extreme contrast of bright and pitch black is both unrealistic and off putting.
I hope you aren't off put yourself by my wall of text, but you know the saying, lots of critizism is a better sign than none, or maybe I just made that up, but anyways you are improving for sure and I hope you will heed and find some of my advise useful so that you may become even better.
