There's not that many of them actually.
You could try the artist named Bacon on pixiv, he do great decomposition stuff, actually he's the goat of this kink.
There's other artists who did some decomposition :
-yahomayo(banaba) : a bit of maggots and light decomposition in very rare artworks
-nrav9lh27 : very good heavy decomposition in some rare artworks
-kittychan : some rotten in some rare artworks
-cmoon : nice decomposition in some rare artworks
-masa1093 : nice decomposition in very rare artworks
-harasaki(原崎) : some top tier decomposition in very rare artworks
-soemele : some medium decomposition in some artworks
-shion(しおん) : some good heavy decomposition in some artworks
-nom-nom(诺姆·诺姆) : some medium decomposition in some artworks
-kitamurapenta : light decomposition in most of his artworks
-veryred(とてもあかい) : nice decomposition in some artworks
-e254e : heavy decomposition in some rare artworks
-Xiug174 : medium decomposition in some artworks

That's all that comes to my mind and note that these artists are not specialized in decomposition with the exception of Bacon.
But what you should really do is to edit some artworks to turn them into heavy decomposition (that's what I do), it takes time but the result should look good (not so hard to do).