This image is a texture from a secret room found in the map pl_marewater versions b4 and above, summarizing the effects of liquefied australium on teats. Part of a canceled ARG that went into detail about it, who was doing it, which mares were being tested and the end goal. Some clues and puzzle pieces from the ARG are in this image. There were more maps that went in further, however those secrets were removed in later versions due to misunderstandings and good fucking lord just ignore it and play the map normally after the first discovery holy fuck, marebowl sneed wouldn’t exist if this was the case.
 
Want to see what it used to be? Download these TF2 maps:  
koth_appleacres_b10: https://www.mediafire.com/file/kssn2g4bnfql66w/koth_appleacres_b10.bsp/file  
pl_marewater_b5: https://www.mediafire.com/file/cg2dleh67zwl1fq/pl_marewater_b5.bsp/file  
cp_marebowl_b1a: https://www.mediafire.com/file/zeu3pxj9eda4wp9/cp_marebowl_b1a.bsp/file
 
Hint for beginning: Capture point and hit all pony faces on posters.  
pl_marewater button locations are in appleacres  
Hint after marewater: hit shovels that used to exist in the original cp_dustbowl
 
These intersects with a minecraft server that contains books with more lore and hints, which right now are impossible to get normally.