Well Dan at Brushwood Nursery sells a pitcheri hybrid that has an interesting seedhead. Here is a picture of the flower (two flowers on far left).
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Here is the url to it on the Brushwood website. Just copy and paste it into your browser.

http://www.gardenvines.com/catalog/clematis-pitcheri-hybrid-p-263.html

Sold out for now but will probably be available this fall.

Don't have a good picture of the seedhead but it looks very similar to the seedhead of the regular pitcheri which is another great purple flowering clematis. I am providing a link to a friend's website showing a picture of pitcheri the species and there is a picture of what the seedhead of it looks like. Quite a few of the US native clematis have interesting seedheads in my opinion. You may want to check out the seedheads on glaucophylla, viorna, texensis, and the others listed on the link. To me they are shining stars that are grossly underutilized and all have interesting seedheads.

Here is a link that might be useful: Pitcheri seedhead

Roguchi is great, flowers all summer, seedheads more interesting than shown, very pretty. {{gwi:246176}}

Here is a link that might be useful: {{gwi:596856}}

Forgot all about Rooguchi altorama. Thanks for mentioning it. Just realize that it can be a mildew magnet in some gardens. It certainly was in mine until I discovered a mildewicide that works for it and several other clematis that get mildew in the garden.

ohh...didn't know about the mildwew, i don't have a problem
with it here in MA....otherwise, a very easy clematis...