Hey Erin, nice work done on your recent attempts on BG. Love the colors and textures you use. Definitely got improvement. Well, here's some comments and opinions. Coz I'm not very good with explaining with just pure words thus i took the liberty to edit from your image, hope you dun kill me for that.
First thing first, composition! I can't stress the importance of that. Coz a composition can influence the viewers to react towards the intented mood you try to bring across. It is also a good way to lead the viewer's eye towards what you want to show. When i saw your BG, the first thing i notice is your 'tank thingy' at the center. If that is what you wan to focus, you definitely got it! Then I after swirling around, i saw that small man at the far end. Immediately i feel that there is a story in this pic. That is another one plus point you got it in. Thus, what i would do is the make that point scores more. I pull the tanks to the lower left and uses the few diagonal lines you got there and put them towards the man, which is now at the top right hand corner. Remember the rule of thirds? Yes!
The second thing I notice is the uses of straight lines. Not that they are bad, if you wan to illustrate a very artificial place and a place very narrow and tiny, straight lines are good. But it will be better it you slant them a bit and try not to let them appears parallel to the edge of the image. Becoz doing so will stop the flow of the viewer's eye.
Perspective as you all know must be correct. You did a pretty good job there. Did a bit of minor tweeking there for ya.
And the rim lights! Never forget those near the tank. The tank give out light thus the metal frame that holds the tank will get the rim light. You can see from the edited images I did.
I am still learning. Hopefully these helps!
