Some people giving their postcards but they doesn’t have any special place for giveaways.What about to have one like lotteries and bingo?under the games and activities section
I think that fits into the section for trades and offers.
I agree with @RalfH. People usually offer them in the trades category and in #games-activities:lotteries.
I agree. For the past 10 years, I have been running this free monthly offer on Postcrossing. Have given away thousands of postcards.
I think I understand why “offers” could be confusing under “trades and offers.” I think maybe when it is under “trades and offers” people think oh, I want something back. But with “giveaways” it would be very clear that the person offering something does not expect anything in return.
I agree @bayankod that the current “Trades and Offers” section also covers offers that are giveaways. You can follow @anon95027724 's example of a monthly giveaway or just do an offer whenever you want. If you want to be clear that it is a givaway, maybe you could phrase the topic like “Giveaway - Disney Postcards” or something like that.
Good luck, and I hope your extra postcards find good homes!