Nice job, I have a few first glance suggestions:
- I see a lot of vias, if this was done with an autorouter, I would suggest hand routing, or at least some cleanup, the free autorouters are not really good
- run a DRC check to make sure objects are not too close or overlapping
- your traces are very thin, you might consider enlarging to at least 8 or 10mil
- some of the text is overlapping vias
- some of the text is very thin, might want to enlarge that, otherwise some houses will automatically enlarge or remove
- depending on how the Pi header mates with the Pi, you might want to not have this board protrude outside the overall PI's boundaries .. but that's just me
Keep up the good work!