Hi Lara, really a CAD tool like MoI is not the best suited environment for things with lumps and bumps in them. A polygon modeling program usually tends to work better for those kinds of things. Or also a displacement brush type program like ZBrush or 3D Coat is easier to make localized bumps since you can paint directly on locations that you want to raise or lower.

Is this maybe similar though? :
http://moi3d.com/forum/index.php?webtag=MOI&msg=7516.1

- Michael