Review of PCB design
Problems with ATmega connections:


You have to connect all supply lines (including AVcc even if you are not using ADC / analog to digital converter)
You need decoupling capacitor near ATmega supply pins


Please read this:

AVR042: AVR Hardware Design Considerations - Application note

Other problems:


you could make some holes for screws
you could optimize component locations and orientations waaay better. Board is messy, there could be only few connections on the second layer. Come on, optimize it.


For example:


1N4007 diode for relay could be placed horizontally, transistor and LED in relay circuit could be closer to that diode