These are so simple and absolutely delicious. You mentioned the smoke salmon in your request. I have never used that in this recipe but I'm sure you could include the salmon in the mixture.
Traditional British tea fare (not really an appetizer, but there was no category that fit.) Curiously refreshing.
Some cooks slice the cucumers in quarters and take the seeds out. I don't bother.
I cater a lot of wedding receptions and this is always a favorite. As another variation, I sometimes cut a smaller shape of bread, put it on top of the cucumber and then pipe the rosette on top of the smaller shape of bread.