show fish decision

hi all this is my first post,

I have a modified biorb 105 with 4 cory cats and 6 harlequin rasbora the tank is heavily planted and there is plenty of hiding places. I would like to invest in some show fish but am not sure what to get!!! i have been thinking about a couple of german blue rams but dont want to upset my peaceful tank. if anybody has any ideas of some show fish that won't upset the balance it would be very much appreciated!!