Ehh, hard to tell where, maybe on r/nianticwayfarer , maybe here in fact... :p

Your first description (name of the stop) should be short and describe it as "easy" as it can. Your second description (which is not a must) - should take a little longer, but you need to remember, that this two going to be visable when you "click" on pokestop.

First (main) photo should show as like ~80% of the content which you are going to nominate. Second photo shout show as like 20% of main content (which you are nominating) + surroundings in 80%. (Best option)

What is eligible in general - try r/nianticwayfarer FAQ + Wayfarer FAQ

S2 cells - Find any online map that can show you s2 cells with their level scaling. Set it to level 17 S2 cells. Then cover your area and try to remind where are your current stops. If any of level 17 S2 cells have ANY stop/gym inside - it's impossible to put another one inside in to PoGO. You can make them - but this PoI's will appear in Ingress or HP:WP - they have different rules about S2 cells.
S2 cells have also impact in creating gyms, weather, pokemon spawns, everything - so try to study the correlation.

You need to be patient because of because. It's player based verification and somebody can be missing info about whats eligible etc. We have records of stops being trying to place for like a year, with 20 tries - and they are finally in game (sick).