CO2 corner brackets are unnecessary, just the holes for mounting are fine. If you do want to keep the corner brackets, please enlarge them slightly (a few millimeters should suffice).
Also, the electronic components of the CO2 sensor protrude from underneath the mounting board by about a millimeter, so could you hollow out a section underneath or raise the holes? Again, just a few millimeters is fine.
The temperature sensor could be raised a bit to give it better access to air flow.
Wind sensor has unnecessary plastic on it. For example, where the slots for fastening are right now, those could be plastic protrusions with holes at the top for mounting.
Also, there should be a hole for wires by each sensor bracket.
Each sensor has wrapped wire, with a diameter of about 5mm.
The thickness of the main base can be reduced, perhaps to about the thickness of the platform that's currently underneath for the arduino and board.
For now, let's leave the platform underneath without holes for mounting so we can be particular about where we want to mount when it's printed, I'll drill where is best for mounting. I have a new board instead of the mini-breadboard that has dimensions of 47 mm x 72 mm so there just has to be enough space for the arduino and that board on the platform underneath.