The mushroom themed free patterns that I found:
Fall mushroom gnome: https://www.ravelry.com/patterns/library/fall-mushroom-gnome-2
mushroom granny square free pattern: https://www.ravelry.com/patterns/library/mushroom-granny-square-2
Mushroom ring square: https://www.ravelry.com/patterns/library/away-with-the-fairies-2
I just found this adorable mushroom amigurumi free pattern on Ravelry. The crochet designer has other super cute amigurumi's on her blog for free... including an adorable rabbit and a mushroom purse. Here is her Ravelry site: https://www.ravelry.com/patterns/library/wilbert-the-mushroom-man
I did a Ravelry search for mushrooms, selected crochet and then Free for the filter option on the left hand side. here is a link to her blog: https://www.cutiepiecrochet.com/blog/categories/amigurumi-patterns