SPCR

My motherboard is missing the backplate which goes where the PS/2, USB, Serial ports, etc are.

I'm wondering if this will affect system airflow (I'm using a Chenbro Gaming Bomb with a 120mm rear case fan and 80mm front case fan) negatively?

What if I use some sticky tape and close the hole up? Will that be ok?

yeah, packing tape or whatever will be fine, i'd just tape it from both sides so one side doesn't get covered in dust and stuff

kind of awkward to tape up though, might be worth calling and seeing if you can just get another one, can't imagine it would be more than a couple bucks... most of the ones i've seen/used are closer to tin foil than sheet metal. dunno about the airflow, if it's right by an exhaust fan then hot air could be coming right back in through the holes, with 120mm + psu exhaust compared to 80mm intake.