Try on all of your favorite shoes and see what parts are not covered (especially if you have a design of shoe you tend to buy). Depending on the shoe you could end up with it hidden, exposed, or mostly hidden. Which would you prefer? For me, hidden is my preference, but certainly not the “correct” one. Make sure the part that shows, if only a portion of the tattoo, doesn’t look like something funny or strange (i have no idea what it could look like but just a thought).
The part that’s sun exposed it will fade more quickly than any parts habitually covered (thankfully for us horse people we’re in boots outside usually!). Another consideration is how long the tattoo will last before needing touch ups. I know hands and feet don’t hold ink as long because of the rapid skin cell turnover.
Depending on the size, single color may be your best bet (hard to do much shading and coloration on a tiny spot). Also, the size will determine how simplified the design must be. When I wanted a design like those horsey window art things, the artist said that it would look like crap in a few years unless it was big, because of the fine lines (ink can look smudged or fuzzy with time).
I wish I had looked into different color options for the ink I got. I know different colors fade mulch more quickly than black but sometimes I think mine looks too harsh against my glorious paleness.
If you have an artistic friend, ask if they can draw one out for you. Get a henna tattoo or even just draw (and redraw) it in permanent marker for a few weeks to think about it (you could just copy a paw print stamp or stencil for the time being). You may find you like the positioning a bit different, or try out a different spot altogether.
My friend has one (a celtic knot) on her back above her bra strap, kind of in the right angle made by shoulder strap and wide strap (girth? Lol!). Initially I thought it would drive me nuts not being able to look at a tattoo without a mirror but i love where hers is, it’s really nice.
You might want to talk with a few artists about it before planning one out too much. They see it all and will know whether or not a certain spot) or design ON a certain location) would be feasible or not.
Good luck! Keep us posted 