This DLC does not add anything to the game. You need to open the file to find it.
Example file location =
D:\Steam\Steam\steamapps\common\Sunflower\Art
To install the DLC, go to you library and find Sunflower. There should be a place to manage DLC. Make sure the box is checked. (I'm not sure if the download button will do this.)
Artwork was done by DemonLordDante and gin-1994.
These artists can be contacted through deviantart.