It could be really difficult to stand out among these big names if you are not already popular.
A couple of popular hashtags are footfetish, feetpics.
Initiate collaboration: initiating collaborations with people sharing the same interests can get you a more follower base, increasing your reach out.
Is It Legally Allowed To Sell Feet Pics Only? Open an account on Pornhub and upload snippets of your videos.