I don't see anything really sensitive like a 24 bit ADC. So there is little to no need to use separate regulators for the relays and the µC. Using just a single supply makes thinks easier as there is no worry about one supply coming up earlier than the other.
Similar I see no need for the opto-couplers, just the transistors are good enough if the layout is no horribly wrong.
Depending in the wire / trace length the I2C interface might want external pull ups. Only the µC internal ones are rather weak. It may work, but just barely. So a board should have pads for external ones, just in case.
It looks like the µC internal ADC is used - so a filter cap at the reference pin is usually a good idea - just in case, one may not need to populate.
The µC usually wants 2 decoupling caps close to the chip - not sure if the layout allows the regulators close enough to the chip. So normally one has caps at the µC and the regulators. Usually there is no need for 10 µF behind the regulators. It's more useful to have such caps before the regulator together with a diode to prevent reverse polarity.