These would make for great terrarium gifts because they're simple, attractive, and easy to maintain.  They won't frustrate the person receiving one.  It looks like you used some sort of lichen and cushion moss?  I'm not good at moss/lichen identification.  It's not often I see moss growing around here.  Very attractive choices though, and green has been associated with feelings of peace and contentment which is why people are encouraged to grow green plants indoors during the winter besides the other benefits.  The reddish veined rock is very cool.  That's a nice choice for a focal point.  All around, smart, easy, attractive, awesome.  Good job!

cool! Nice thing to have in a bedroom next to the alarm clock or something for display.

Very pretty.  when I was a child, we put a little water on the garden and then a  lid on the jar.  The moisture evaporated into the garden bit by bit.