Most natural caves would have rough terrain, not a smooth floor. Try adding rocks, debris, and small cracks.

Here are some cracks to try, and some webs. all these are from the Dundjinni forums.

Cave with Pool-483_cracks_shadow02_dbl-c.pngCave with Pool-1cracks01e_dgw.pngCave with Pool-cracks2_bg_dgw-.pngCave with Pool-cracks2_bg_dgw-d.pngCave with Pool-cracks2_dgw-.pngName:  Cracks_ERN-g.png
Views: 111
Size:  41.6 KBName:  Floor_Crack01_kpl-h.png
Views: 107
Size:  4.8 KBName:  Web_SB-a.png
Views: 105
Size:  48.9 KBCave with Pool-web_sb-b.pngCave with Pool-web_sb-c.png