anything natural will work. Certain fey will be more drawn to certain items. Yes certain fey can be dangerous but you can find ways to keep make it a little safer. One way is to make the door specifically for a type of fey. Research fey & you will find each has it's own favorites for color, drink, food, flowers, etc. Many also have things they despise or work to keep them away. The thing is that all fey can be mischevious so if you have a hard time handling practical jokes, don't invite the fey in. I don't know how you feel about protective spells/prayers but if you do believe that would work as well & can be geared towards only letting in those who mean no harm.
