I just did this recently to remind myself how to do and to let someone else know how it was done
![Image](http://gimpchat.com/files/1831_bumped%20beauty-portrait.jpg)
My workflow was
Selected the image of choice. Add a background - (can be whatever you want but a similar pattern all over is probably best).
Selected Filter > map > bump Map and chose the image as the input, while the pattern layer is selected. Used default settings except elevation at 54 and depth at 37. Moved sliders to get what I wanted before clicking ok
ps. image can be desaturated and then lightened with curves before bumping but is not necessary.