We had our two-car attached garage converted into a full therapy/classroom/playroom with an accessible bathroom and changing area about 18 months ago. The entire cost was covered by the wish organization "Wishing Well of Texoma". Our plan is to eventually have a lift system going into the bathroom and changing area. That part will be covered by Medicaid, we just aren't ready for the construction aspect of it.
The room is heated and cooled by a stand-alone "window" AC/Heater unit (much like what you'd find in a hotel room). The unit works excellent and prevented the need for additional duct work to be done to the addition.
Once the room and bathroom were completed, my husband and I did the decorating. Aside from the educational toys, books, and switches, there is a tall table that allows for clearance of the special needs wheelchair (which generally sits up high than a standard wheelchair. There is also a texture board attached to one wall for sensory play for visually impaired. Additionally, we chose a wood laminate for the flooring to allow easy movement of both the wheelchair and the gait trainer.
The changing area was super easy. It is about five steps from the shower - just outside of the bathroom. We selected a solid wood (heavy!) full-size dresser and padded the top. There are six deep drawers that hold everything from diapers and towels to tracheotomy supplies and catheters.