Here's the bit I mean.

 

The Blend node circled in red allows you to choose which to use. If the Blend value is 0 (as it is in the screenshot) then it is all procedural. If it is set to 1 then it will take whatever is in the Image node that's sitting next to it (which should be the bump map texture, of course!). Any value between 0 and 1 will take a mixture, with 0.5 being exactly half-and-half.