Update
updated the prison set - columns for 2 great prison wallpapers, the grey one and a creamy version of the white on (by me). because the catalog is starting to get full, i've prepared a second version: the bars just appear on the standard version, while the wallpapers are seamless only. you could use theme for a hidden exit, too. As columns, they can also support glass roofs for decks (the blue part in the picture is not caused by my object recolor, just a graphical glitch).

I'm using .rar for this file because of its size, i'm sure you find a way to unpack it.

Prison Set 1 appears on both windows and is for users of just one wall-window set
Prison Set 2 - the bars are standard only while the brick walls are seamless only. This is for those who have both wall-window sets

using both prison sets simultaneously will cause incompatibility, this won't harm your game, the worst thing that could happen would be the recolors appearing on the wrong set.