Hi Zymon,
If you are thinking about something like a bas-relief, it seems like there are undercuts in that picture… using a single alpha for the entire object would not generate those.
ZModeler could be used to build a base shape, then subdivide and add detail to it. You mentioned having Sketchup experience, and while ZModeler is far from Sketchup in many ways, it has greater similarity than the other tools, so ZModeler might be a place to start.
Although I’ve had ZBrush a long time, I’m a novice in building a form up with the sculpting brushes alone. I know there are a lot of people around here that can, so hopefully you will get some direction here if you want to try that method to compare to ZModeler.