My frog/reptile room is in my basement with concrete floor. Use racks to keep your vivs on. Is it insulated? I insulated my and with the door closed and an oil filed radiator for heat, I can keep it easily at 74 deg during the winter.
Other suggestions would be sink and a table to use.
For my frog room I am using black bakers racks. They work great allowing for almost infinite shelf adjustment. I can use zip ties to secure power cords and misting lines etc. The shelves will bow a little so I purchased 3/8" ply at $10 a sheet for added support. Lowes sells black T8 shop fixtures for $12 each. I only use one bulb in the fixture. This is plenty of light for the plants. I also hung nice power strips to the racks the plugged them into timers.
A RODI station might be nice to have if you are able to run a hose to the garage you can have a reservoir inside with a spigot. so you have accesiblity to fresh water at all times. its nice wether your hand misting, refilling misting reservoirs, or doing water changes with tad containers
I only have a 5 gallon container with spigot, but wish it was larger! they make food grade a 55g barrels that are white, and pretty cheap.
Looks like you're building two new walls. You could put split receptacles along the walls at a convenient height, with one circuit being 24 hours, the other controlled by a timer. One for critical systems, the other for lighting.
Depending on how fancy ($$$) you want to get, a Heat pump or MiniSplit would be the most cost effective options.
The Mini Splits probably meet your need the best as they are less expensive and designed for a small space. They will save you a lot of money in the long run over a space heater and provide both heat and cooling for year round climate control.
knocked this out, did it three high, but there was no room for the last light (would have needed 8' 8" ceilings... sorry), also you didnt have enough room for 3 wide of the 24" cubes and the supports of the rack
here is it 2 viv high with 29s instead of 20s since they are the same as a 20, just deeper (you get more viv with out loosing critical space (the frogs will thank you for the 29 over the 20 )
the theory in building the rack is the back 2x4 is lag bolted into the wall then there are front legs to carry the cantilevered weight. will be tough as nails!