There are two bosses and an NPC battle, which is optional along with the second boss who hangs out at the very bottom of the painting. (darkstation.com)
If you want to add the polkadots, add Fabric Medium (so it will be washable) to any craft paint and use the bottom of a paint brush to paint on little dots. (flamingotoes.com)
A blue band at the bottom of the painting suggests the much gentler action of water lapping the shore. (painters-table.com)