Sorry to hear about your redundancy mate, trying to look for a job myself. All the best on that anyway.
On topic, if I was playing I would like to see more assets, SaferDan is right, things like bins, cans, chewing gum ont the floor, crap building up in corners i.e. leaf litter/rubbish. Of course graffiti on the surfaces. Fire extinguishers, signs for the way out, old lighting hanging off, wires broken strewn on the floor etc.
The clock looks like it is in working order, should wreck it a bit. Things like that will deter from the aim of the scene, which in this case appears to be devoid of human maintenance.
Tortilla makes a good point on the plants being to green, maybe make some brown vines, mushrooms, plants which occupy low light areas. As he also mentioned, moss and lichens on most large areas, you have a great base texture down, just need to mess it up as it is to clean in a nature sense... you get me?
To amplify on that, water maybe running through cracks, along the floor onto the track, down the walls, creating rust or mud stains. The roof may collapse from water logging. Roots may be tearing through the floors/walls/roof.
Mate I could go on, but I think you got enough there
Edit: As it is apocalyptic you should think of other methods of lighting other than electrical... there is no one about to run power stations. You could try cutting a hole through the roof to let sunlight in, random fires sparked due to ... god knows what lol. Think out of the proverbial box as they say.