Wall planters are displayed one tile above the bottom of the wall by default, but the game recognizes them as being on the bottom tile, so you can water and add fertilizer by clicking on the wall's bottom tile no matter how high up the planter is.
You can adjust the planter's height on the wall by hovering over the wall's bottom tile with the mouse and holding down the up or down key (default Up Arrow and Down Arrow).
You can adjust the position of the planter contents within the planter by hovering over the wall's bottom tile with the mouse and holding down the mod key (default Left Shift) while holding down the up or down key.
The wall planter sprites can be changed using Content Patcher by targeting the following paths:
aedenthorn.WallPlanter/wall_pot
aedenthorn.WallPlanter/wall_pot_wet
Technical
Requires SMAPI, uses Harmony.
Compatible with Mod Updater for automatic updates.
Code is at https://github.com/aedenthorn/StardewValleyMods.
If you want to complain or ask for help or help me test my mods, you can visit my Discord server.
A list of all my mods for Stardew Valley is available at https://www.nexusmods.com/stardewvalley/articles/895.