Zenram, I don't mean to imply you did anything wrong with the shadowing as some mapping apps like Campaign Cartographer do the same kind thing, that is placing a directional shadow as in your map.
The problem with a directional shadow is that it implies light coming from the sun, and to see a directional shadow on the interior, it means there is no roof.
My two thoughts on shadowing are thus:
1. Most often I use a halo shadow, that is a shadow at the base of the object that is equal on all sides. As if no specific light source is causing it, really more of a way to help differentiate the walls from the floor.
2. If shadow accuracy is important, it would be better to place interior light sources (ie: torches on sconces, roaring fireplace, or hanging wall lanterns.) then create the shadows based on where the light sources are and directional shadows based on those light sources. This would probably be the most accurate way of doing it.
Unless I go to the trouble of placing light sources, I usually only use "halo" shadows, as it is only a convention to help a viewer know what is floor and what is wall.
I see no specific bevel issue, though, I use bevels all the time in my interior maps.
Final point, if this map was going to be used in a VT app, like MapTool or Fantasy Grounds, aside from possible use of halo shadow, you don't want to place shadows at all, as the players may have a light source in their hand and the respective shadows are based on that light source and shadows will change as they move around your map.