Recomend a sedum

There has been some progress on the living picture with the frame now ready to go.  I have made it in two sections, an inner box for the soil,  and an outer frame to look a bit nicer.

These were stained to match the wood that forms the actual front of the frame, and a wire mesh put across the front to hold the soil in.  This is it all ready to go.

 So the frame is done,  I have most of the plants ready,  but still looking for a few things to go in with the echeverias, sempervivums and a little agave utahensis.  I think the final design will be a reef so following up on a comment in the earlier post I thought a sedum or saxifrage may work for flow between the different plants.

I have mentioned before that a lot of my plants come about through people mentioning them or seeing them in other peoples gardens. I thought this may be a good way of finding a suitable plant for the picture. So get your thinking heads on. A bit of red would work well with the other plants,  probably smaller leaves to allow it to weave nicely between the plants (it is not a huge frame only 50 x 35cm).  It needs to spred by not in a way that will need too much pruning.

So any suggestions of a good sedum or something else you love that would fit? I can then have fun looking them up and who knows then trying to track them down.