yes there is an 8-QAM. but, i don't think if it is still being used nowadays.
anyway, do you have a circuit of 16-QAM transmitter? i would really appreciate if you share it because i need it for my project. our teacher did not really specify what type of QAM to use.
The block diagram from Tomasi's book (Advanced Electronic Communication Systems) should help you, theres an 8-QAM block description and can be easily
designed by yerself