"Nothing for entertainment or changing clothes"?
OK, frame challenge. This is not a correctional facility, this is an arrest cell in a military installation. People will be held for interrogation, until execution, or until transported off elsewhere to be interrogated and / or executed. There is no "VIP" status either, Leia didn't get to take her luggage and was not given a change of clothes by the Imperials. Indeed she was scheduled for execution (as C3PO pointed out earlier), so why bother?
If you look at a military arrest cell today -- any country, really -- what you see is a bunk, and a stainless steel loo in a corner, no more. No table, no shelves, no chair.
We don't get to see a loo in Leia's cell, but we don't get to see the whole cell. There might be one in the corner we don't get to see, there might be one behind some kind of panel (the novel text posted by Valorum does not tell us that either, it just states there were no loose panels to be pried off). Perhaps they walk the prisioners to the head on schedule, as to further drive home the message: We are in control here, Rebel scum.