mood theme is very fun feature here ! with paid time on account , can even make custom one . some people use pictures from favourite media , others adapt free to use emoticon art , or just anything which strike fancy . of course , can also pixel art ! especially fun for sona characters , really bring personal flair .
but sometimes , not really sure where to start with that . well , here is kossai method . :P
this apply for specifically
static base pictures . animations still use mix and match process to create base , but then bring into separate file for ease of animation .
bottom layer group - basethings that will
never move or change . for kossai sona this is head shape , ears , and beard , as well as basic white outline layer for visibility on dark themes .
next up layer group - eyes
specifically , in 4 layers , from bottom to top : sclera colour , iris colour , pupils and highlights , and outlines .
some moods do call for iris and pupils to move . to prevent clip oddities , both these layers set on composite mode
clip to backdrop . this is why eyes come in separate layer group - otherwise , iris movement would clip onto skin as well .
assortment layer groups - facial modificationskossai sona do not have mouth or nose , so this come in 3 subcategories : eye mods , eyelids , and facial flushes .
eye mods cover any kind of eye which is not standard : blown pupils , closed eyes both upward and downward , wink , spiral eyes , squeeze shut , bill cipher reference , and blank slate . most of these also include background of skin colour to cover standard eyes , but could just as well choose to hide eye group .
eyelids cover tweaks to eye shapes : sad eyelids , angry eyelids , tired eyelids , cheeky eye smile , devious squint eyelids , and twitchy eyelids in 2 forms .
facial flushes include blue sickness , and yellow blush . for each kind of flush there is 1 full layer , which do not accomodate any eye shapes , and then duplicate and erase as necessary to conform with other shapes . not elegant , but functional .
last layer group - floatiesobjects which help to clarify emotion . specifically , kossai floaties fall in categories of punctuation , and props .
punctuation include hearts , ellipsis , ellipsis and heart , exclamation marks , question marks , interrobang . these work for intensifiers - say want difference between
angry and
irate , but not sure how to
make different . exclamation marks , or perhaps censor bar , could intensify expression , without need to make something fully new .
props include rainbow paint pour for artistic , dirt cover and leaf for dirty , stanford pines glasses for nerdy and geeky , frost cover and icicles for cold , and finally ,
out of order post-it note for exanimate .
finally , here is some example of how kossai put these in action :

base face and blown pupils create curious .
rainbow paint pour and eye movement create artistic .
stanford pines glasses and hearts create geeky .
squeeze shut eyes , frost , and icicles create cold .
again , animations such as these :

belong to
separate files .
devious , for example , use frames of standard face , standard face with bill cipher eyes , and then various eyelids to create blink cycle .
crushed meanwhile use sad eyelids , warp perspective to " flatten " sprite , then draw rock to fall into frame .
hopefully this is of some kind of use , or at least interest to others . :)