I don't think there is anything wrong with naming a horse. When I got Scout, his previous name was "Redford", lol, it TOTALLY didn't suit him at all!!!
Then with Halo, can you believe she was 2 yrs old and they didn't even have a name for her. I asked them what they called her, and they just said they never called her anything, I was like WOW, really???
Anyways, I really love Tsima, it really sounds unique and is very pretty. I also love the meaning. I can't wait to see pictures.