CodePen won’t let me upload graphic files without a Pro account.
Yes, CodePen Projects are basically a paid feature of that platform. If you really want to use them, yes, they cost money, but you only need (free) Pens to do the FCC projects (you just need to host the media somewhere)
As @DanCouper stated, you need to host your media with another service unless you want to upgrade to Pro account.
For my FCC projects I am using https://cloudinary.com/
It’s free with optional paid upgrades if needed.
I did look for related posts before posting, but found none. At any rate, I don’t know how to host at another site. Is there a tutorial, or post, on FCC covering that subject?
There are lots of free image hosting websites. Don’t use Imgur as it’s against their terms of service (so Codepen blocks links to images hosted on Imgur), but most other ones work (Cloudinary is good)