This is a relatively simple image to create.
The objects are mostly basic shapes with small modifications. Much of the effect comes from using layered textures - a technique used extensively in this scene.
All the textures in this scene can be found in the Total Textures collection.
We'll start with the floor. The basis is a nice map of some terra cotta tiles which have been applied using planar uv mapping on the Y-axis. A greyscale of the same image is used in the bump channel. This looks OK but repeats are clearly visible - particularly a line of yellowish tiles running from top left to bottom right.
To hide the repeats and add another layer of grime to the floor, I added another texture map (and corresponding bump map). This is pockmarked concrete. To allow the tiles to show through from underneath, I used yet another texture as an alpha map - the tiles show through in proportion to how dark the alpha map is at any given point.
Using the solid modelling mode of your 3D package, you can set the u & v scale and position of your grime map to get the effect you're looking for. Remember that the concrete texture will show up where the grime map is lighter. Here, I have set the grime map so that plenty of dirt shows up where the walls meet the floor.
The corresponding concrete bump map and the same grime alpha map were used on the bump channel to add the extra pockmarks. Note that for more complexity and interest, I used the alpha map at a different scale in the bump channel with the result that some of the pockmarks appear outside the dirty areas (you could even use a different bump map too). The colour map does not always have to match the bump map!
Proceed to page two, to learn more about texturing the rest of this scene