As long as you're posting content of some kind I don't think you've got much to worry about 
What my team and I are doing during our first hiatus (mostly so we can get an actual buffer of pages), is bringing a few other artists we know to do a guest story. It's short, but will feature stuff our viewers won't get to see for a bit. So it'll be exciting for them to see more of the world and the characters we always get asked about.
For other holidays, dude, just some nice splash/pin up (as in just really pretty pictures, not titillating stuff), can do wonders too! Stuff like this:
This one was for the winter holidays
A fathers day post we did with our clean up and character artist and Havana. She talked about how her dad inspired our leads father, Toshi. 
This was a new years image we did, and one we use for our thank you posts (oh jeez...I gotta catch up on those!)
I think the development art is a really good idea as well. People love flipping through our dev art book at cons, I'm sure they'll love seeing your early work too! 