Artist’s comment:
 
So many headcanons I should work on, but I decided to take my first go with this one.  
Simply cuz due to some not so former episode.  
Seriously, why have ponies even invented these rings they don’t have fricking fingers?!  
So I decided to not tag along with this ring agenda.  
In this headcanon, ponies don’t do engagement rings.  
They do engagement gems.
 
There are two variants to choose from. Either the gem resemles the other one’s cutie mark (LyraBon) or their representative color (TwiBurst).  
Usually the cm verse is choosen by proud ponies, who want to show their specific love to the world, while the simplier color version is mostly used by those humple, modest souls.  
Unlike with the colors, where there is still enough room for speculations, the cutie mark gem ties two specific ponies and can sometimes be viewed as a mean for possessive behaviour.
 
The ways of wearing the engagement gems differ pony by pony. There is no said rule for how to wear or show it.  
Still, majority of population goes with a brooch, that can easily be attached to their everyday wardrobe (AJ). Other popular options include earrings (BonBon), rubber bands or ribbons to tie their mane up with it (Twilight), decorated headbands or simple or less simple necklaces (Lyra).
 
 
I guess that’s about it for now, I’ll add more if I ever come up with something else worth mentioning. xD