- Your reset network is wrong. ATMegas need a resistor pulling reset up to Vcc, and optionally a cap from reset to ground.
- You need decoupling at the MCU. 100nF or so, one at each Vcc pin, as close as possible.
- D7 could be problematic. Vcc is connected to the ISP header so that the programmer can detect the target MCU's operating voltage and set its IO levels (it may actually power the target side of the IO level shifters in some programmers--not sure). D7 will prevent that, so will prevent at least Atmel's tools from entering programming mode. Third party tools may not care, especially cheap ones. If your programmer will be supplying target power while programming, then D7 is fine.
- How much current are you planning to switch with those transistors?
-Your ground plane is pretty carved up. Consider spreading the legs of your diodes to allow the ground plane to flow more freely. Also consider orienting the diodes (and maybe some wire links) vertically and preferentially route traces horizontally (or vice versa) to provide a more contiguous ground pour.