Pondering the Bathroom

Tongue/frame progress is going so well - I need to start thinking about the bathroom.  I am going to have a toilet and some sort of shower.  Starting to think about it all.  Here is the space I have to work with:

The old water heater (in green) is coming out and will be replaced by an on-demand water heater.  I have all that space from the water heater towards the back wall and to the back/left curbside.  The toilet was in that back left hand corner and the right hand side was a closet.  Will be pondering all the possibilities...