Cool. I'm glad you like it.
Every home, different recipe, so it's ok to replace stuff with what you have. For example some recipes ask for butter instead of lard, or margarine, or vegetable oil. The walnut/poppy seed filling can be mixed with jam, ground apple, honey, sugar... Some people add raisins, some leave that out (in my xp people tend to have strong feelings about raisins, positive or negative). Some uses cherries instead. I heard about chestnut, chocolate, apple-cinnamon, and even coconut fillings too. But the traditional is the walnut and poppy seed fillings.