Continuing with my example...
Let's say you wanted to add depth to the brick texture, here's what I'd do:
#1 - apply the wavelet decomposer. Make a copy of the residual layer, move it to the top, invert the colours & desaturate:
#2 - apply emboss + maybe a slight 1px blur on the copied layer
#3 - set the layer mode to grain merge and lower opacity, and voila, you have more depth:
The new layer acts as an extra layer of grain. By taking the residual (which contains only the colour information of the original brick wall image) and inverting it, we get a layer where the mortar is dark and the tiles are light, which makes for a perfect bump map for the brick wall. Then by applying emboss on it, you get a sort of bevel that follows the shapes of the brick wall perfectly, therefore increasing the depth of the wall. By setting the layer on top of all the other grain layers, it also affects the paint, therefore making the painted areas follow the depth & texture of the brick background perfectly, while showing a different colour.