MicroATX doesn't define the size of the cooler, it defines the size of the motherboard. With that said, nearly every cooler compatible with Intel's socket 1155 will work with your board, assuming your case has enough size for it. Noctua's NH-D14 is generally regarded as the best air cooler, though it's size may cause issues if you have a smaller case to match your smaller board. A smaller air cooler such as Cooler Master's Hyper 212 Evo will be a better fit inside a smaller case while still offering enough cooling for an overclocked chip. An all-in-one liquid cooler like Corsair's H60 will fit in just about any case that has a 120mm fan mount in the top or back of the case.
The best cooler to pick would mostly depend what case you choose and how much room it offers for CPU coolers.
Regarding size though, the CPU is closer to the DIMMs in an mATX board, so the size of the cooler may matter too, as large coolers' fans may cover the RAM in the furthest slot. So are there recommended coolers that won't cause a problem with the RAM in the furthest slot?