To make the black windows appear behind the player, I'd use a scenery file (blank.bmp) coloured black and "set to black".
To make the other section you pointed out appear behind the player, you need to print screen it (at 100% zoom) then paste them in paint. After this, use lime green (Red: 0 Green: 255 Blue:255), the colour for transparency in Soldat, to make everything but the section you want invisible when in polyworks/soldat. Then resize the image so you don't have any unnecessary transparent pixels in the image. Once your done, save it as a png in the scenery folder and add it to your map at the desired position making sure it is "set to back".
There is two ways you could make the water fade into the background. One would be to simply use a scenery file which fades from 0% opacity to 100% opacity like fx_li_beam.png set to a colour as close to the background colour as you can get it, set over the top of the water.
The other way would be to edit the actual image to suit your needs using photoshop, paintshop, gimp or something similar to make the image fade to 100% transparency. I'm not sure if you'd need permission from the creator before doing that or not though.
You might want to add a few bushes crates or other scenery suiting to the theme. I know it might not actually be there in real life, but it'll make the map play better. That's unless you're trying to make it more of an art piece than a fully playable map.
Looks good so far.
