stack them on a wooden dowel...there are so many things you can do...add greenery in between each pumpkin...you can put them in a pot like a topiary and use Spanish moss around the bottom...
Here's a step by step tutorial! https://www.cravingsomecreativity.com/halloween-stacked-pumpkin-topiary/
I love this one.
Here are some great ideas!!
Here are 6 ways to do it. https://www.diynetwork.com/how-to/make-and-decorate/decorating/6-ways-to-make-a-pumpkin-topiary-pictures