Wow, this is a really great painting, and frame too...thank you for sharing :-)
Yes, many gods have become "Saints", Christian missionaries used all possible tricks to turn people into Christianity ( they were converting people from 6. to 10. century). They also burned old oak trees that were sacred for Slavs, but some of the oaks older than 1000 years have survived. My grandmother told me that as a girl she was playing around old oak near village where she was born (southern Serbia) .That oak was called "The Record" ( Zapis ). She told me that there was an old custom of burning dead people and spreading ash around the oak so that the tree absorbed the dust in itself so that the person (spirit) continues to live in a tree. And when someone got sick they took a branch from the tree and burned it in the house so that the smoke filled the house and pushed the evil ghosts out of the house. Also when they hear a bad news or need help, they have been knocking on wood ( tree) to wake up sleepy ancestors who live in the tree (wood) and ask for help...