I have an 80mm case fan mounted to my electronics enclosure, at the very least it keeps the heat sinks very cool. I haven’t really pushed my machine yet, however, so I don’t know how well it will cool the electronics when the sled is in one of the high-stress locations on the bed. I have documented my fan mount here: Arduino/Motor Shield Enclosure (Picture Heavy)
Not sure how much power the board can take but as an alternative, I just crimped the fan to a 12v power supply and plugged it into the same power strip that runs the electronics. That way the fan turns on with the machine and it doesn’t take any power from the motor shield.