This response is just in general and not directed at you: If you can source images that for unrestricted use you'll be fine. If an image does not state that it is CC or free to use then you should assume it is not fair game for 'fair use' as Steemit is a commercialized platform. If someone that owns a photograph would like to pursue a copyright infringement case, it'll be impossible to delete your post unless you could affect a customized hard fork on the Steemit blockchain. Pixabay is a source that has such images that are available for use. If in doubt, read more here: https://www.law.cornell.edu/uscode/text/17/107
Lest you be tarred & feathered!
I either use pixabay or my own photos. And you're right, after 1st payout it' impossible to remove the photo.