Love? The best in my opinion and the most universal symbol for love (also in Poland) is a red heart. The second place I would give for red rose.
Strength. In Polish culture 'dąb' (oak tree) is associated with strength. There's even a saying in Polish: "Silny jak dąb" (Strong as an oak). Another Polish strength symbol is Mariusz "Pudzian" Pudzianowski - known ex. strongman ;)
That's a great saying! I like it!! Is there a pic of an oak? Is it a Polish oak? Sorry if This sounds strange. I'm looking to add these two symbols to an existing tattoo that I have. The saying is powerful!