This guide contains a list of all the accessories you can unlock in Sonicomi.

There are three different ways to unlock accessories:

• Story Mode
  
• Ouka Shop
  
• Photo Shoots

Story Mode
You will get all these accessories as you play through the story mode to get all endings and outfits.
Just as with unlocking outfits, the different accessories are unlocked based on the choices you make and your position on the grid.

Ouka Shop
Even more straightforward than story mode.
Simply get any ending to unlock the shop and then you can buy the accessories with the Sonicoins you get from photo shoots.

Photo shoots
To get accessories from photo shoots you need to photograph the sub-targets in the photo location.
For example in the Beach location you must photograph the seagulls, dolphins and the weird flying machine. You will hear a specific sound when an accessory drops, it's quite distinguishable from the other photo shoot sounds.
Some of the accessories are tied to a specific location like the Gothic Ribbon which only drops in the Café.
But others are not tied to a specific location and seems to be able to drop anywhere. From my limited testing it seems that this is true for the easy to get accessories, while the more hard to get ones are location specific.
This means that you might find a specific accessory in a different location than I have listed, but if you are missing a specific accessory at the end of the game I recommend to hunt it at the location I have listed as that is a confirmed drop location for it.

Just don't give up when you're hunting the final accessories. The drop chance seems to be random and it can take 1 shoot or 30. Just keep at it and focus on sub-targets.

1.5 - Updated last 5 locations. Guide is now complete.
1.4 - Updated 6 locations. Only 5 left. Special thanks to Sinful Sorcerer and GR3YL0TU5 for providing a couple of locations.
1.3 - Updated 36 locations and fixed one error (PomPoms). Only 11 locations left
1.2 - Added a section about unlocking accessories. Fixed an error.
1.1 - Updated 43 locations
1.0 - All accessories and their designs listed. Many locations still missing