Rodrigo's "Invocation and Dance" is one of my favourite pieces with tremolo. There are lots of allusions to De Falla's pieces, Miller's Dance, Nana, Fisherman's Song, etc.
Another one is Koshkin's "Merlin's Dream". This one requires a fair bit of string crossing - both up and down during the tremolo section.
About 6 years ago I made a web page which listed all the tremolo pieces I knew of. I haven't kept it up but it is still there. I won't use a direct link but if you google for (pamilearner tremolo list tripod) it should come up.