This texture was generated in Filter Forge, a Photoshop plugin that allows you to create your own filters.
This evolved like the organic material it looks like. Designed for putting realistic patina or organic looking 'sheen' on objects.
But... it does look pretty frog-like in it's native preset.
Note: when exporting bump maps, you can use the TONE adjustment to sale the landscape elevation
:)
grunge, frog, dirt