As Jenbel said, there's quite a bit of variety across the region. If you're interested in walking, or even if you're not, http://www.walkhighlands.co.uk/ gives nice information about the characteristics of the various parts of the Highlands, with some photos.

Depending upon where you are in July, be prepared for the dreaded highland midge. Do a little research, and bring your anti-midge supplies, because the Highlands are definitely worth the effort.