If you don't have some project in mind that scratches an itch, I'll give you the same answer I give my peers and juniors: Do something different that builds your skills.

There's terabytes of open data, tools and tutorials available on the internet. Build a tool that scrapes the FCC database and allows people to research radio station call signs. Dig into some of the NASA archives, do some image processing. Check out the growing infestation of humans, chart it on maps with the help of US Census data. Build a local weather application. Get a cheap SDR USB radio and build a different GUI to control it. Find your bank/credit unions quarterly posts on their respective government agencies websites and plot how much money they make from fees vs margin. Build a calculator app with advance functions. Tailor it for small business like a roofing contractor. Do any project in a different programming language, then port it to a third. Work through the problems at Programming Praxis or SICP. Tweak a game through Lua or whatever tool kit they offer...