I've been putting a ton of time into the castle, I just about completely ranked up from a 35 to a 36 just by building on it. I might take some pictures but it would be crappy cellphone shots of the tv since I'm on the Xbox.
I basically built an entire second story even with the top of the castle walls where all the settlers and Minutemen live. I then built an elevate platform over all of that that I live. My house has a bathtub full of money (not fun to drop prewar money out of your inventory one at a time), a disco ball, pool table, multiple tvs, magazine racks, and a bobblehead stand. On the ground floor of the castle is where the crops are, vendor stalls, and a bar for everyone to hang out after work (the NPCs really do hang out at the bar for awhile after their work is done for the day). All of that guarded by tons of laser turrets, regular turrets and artillery. I closed off the blown out walls so the only way to get in is the front gate which is lined with turrets, nothing would survive a frontal assault.