Where are Desktop Viber Avatars located on PC?

If you want to see all the avatars / photos that your Viber contacts use for avatars (even old ones) then you can find big sized images here (this is only for Windows):

DRIVE:\Users\YOUR WINDOWS PROFILE\AppData\Roaming\ViberPC\YOUR PHONE NUMBER\Avatars

so for example if your drive is C, your windwos profiel is FooUser and your phon is 555-55555 then you can find it here:

C:\Users\FooUser\AppData\Roaming\ViberPC\55555555\Avatars