We got a king size bed. Best decision EVER. We've been wanting one for a while, but then when my belly started growing, the decision to get one became more important. :) Also, it'll be good for little baby snuggles too.
We purchased one a couple weeks ago and my mom and stepdad helped me make a headboard for it! I found a tutorial on pinterest (just typed in DIY headboard tutorials) and followed one I found there.
As long as you're willing to spend a few hours building/constructing it, you'll love the outcome and it's going to save you a good amount of money. Upholstered king sized headboards ain't cheap, y'all.
We used MDF for the headboard, an eggcrate for the stuffing and a drop cloth for the fabric. The total cost was under $50!