Daniels118 is right, if you use a wall or a floor then the texturing is not changed to squares, that might be a good solution for you.

Some tricky things to remember when you use a wall:
A (new) project with no levels added exports a wall with the exact height you gave the wall.
The same project with a level added above and the same wall on level 0 will export with it's height + 0.1cm.
A wall on any level that has a level beneath it will export with it's height + the floor thickness.

When you use a floor:
Make sure you uncheck the ceiling checkbox before export
With no levels added the resulting object will have a height of 0, i.e a single flat face. Perfect as a 'texture' for what you want.
In the 2D view the quality of the resulting floor texture is not that good compared to the display quality on a wall. In the 3D view and rendered photo's there is no quality difference.
You can use a floor (room) as is, so without exporting, but you will have to add a level for each shelf height to get the elevation of the floor. Make sure you use a floor thickness with the thickness of the shelf and uncheck the ceiling checkbox. To add a border you will have to add that to the level below the floor and elevate it so it levels with the top of the floor. This is a cumbersome method but it probably puts the least pressure on your system resources since only a single texture tile is repeatedly used where exported floors each get their own texture image.

When rendering a photo there is a little difference between wall/floor but not in the sharpness of the texture, mainly in the coloring.

You will have to try it to see what fits your purpose best.