Thanks, Sapiento!

loogie, it's a nice workaround, I just have to make practice 'cause in some regions the transition from layer to layer is not smooth. But thanks, your advice pointed me in what I think is the right direction to draw bigger mountains. I just merged the various levels, before...
Just out of curiosity, would you judje GIMP and Inkscape better softwares to draw maps? Are they any lighter? 'Cause I like Photoshop, but my hardware is screaming pain!

Sorus, no problem. Pasis' and Tear's are the two tutorials I'm using to make practice, and they are great. Give them a try! And yes, I'm full of information! Oh, crap, the Intelligence! Sorry I have to go!