We apply an analytical approach for determining the near-field radiative heat transfer between a metallic nanosphere and a planar semi-infinite medium with some given surface structure. This approach is based on a perturbative expansion, and evaluated to first order in the surface profile. With the help of numerical results obtained for some simple model geometries we discuss typical signatures that should be obtainable with a nearfield scanning thermal microscope operated in either constant-height or constant-distance mode.