What are flexi-hedras? To give them their full name of Flexible Polyhedra may shed some light but to fully describe them I'd have to say that they are geometric solids (i.e. dodecahedrons, icosahedrons etc) which are made up of triangular prims (Primitives are the building blocks of Second Life) which make use of the Flexible Path feature within Second Life. A series of scripts controls the motion of the objects prims and several settings are adjustable.
To display a photo of these objects would defy logic as they are by definition moving sculptures. For this reason I made a few short videos at the time of their first conception, only on one other occasion did I take another video and that was at the Second Life 3rd Birthday (SL3B) Art Exhibition [nag me some and I may make some new videos]. You'll find these videos below.

Flexible Icosahedron

Flexible Dodecahedron

Flexible Great Dodecahedron

Flexible Small Stellated Dodecahedron

SL3B Exhibit
Well perhaps a few snapshots won't hurt:

Flexi-hedra display at Second Life's 5th Birthday