Someone was asking on TMP whether BTD Romans fit with Tin Soldier's. I have a few Tin Soldiers and have shot a couple above (2&4) next to some BTDs (1&3).
I think one could just about get away with it, although I find the Tin Soldiers crude by comparison with the BTDs (big heads and stocky legs; something of the dwarf about them. And that horn!). Having said that, I have 6, they are painted and I might just base them up.