From their announcement:
This week sees the release of a new theme of bases, the Desert Mesa.
The Desert Mesa range represent an arid, wind-sculpted landscape. Multiple layers of cracked, lightly textured rock combine to form an appealing and easy-to-use set of bases. The fairly flat surface makes it simple to attach figures, with more variation on larger bases for visual impact.
This week sees the release of the Round Bases with all the options for Round bases we sell covered. The Square bases are released next week.