Hi Deb, there are so many cool things you can do with old decking boards. Make sure it is not pressure treated before making any projects for in your home. If it is old, untreated wood you could make shelving, tables, signs, a headboard. Here is a headboard I built (with new wood but you could easily use old weathered wood... http://www.recreateddesigns.com/2015/12/diy-wooden-headboard/
Beautiful ... thank you. A very good idea!
As long as they aren't pressure treated, you can use them for a plank wall or many other projects. I did this in my workshop with old fence boards, which could be done with deck boards as well: How to Use Old Fence Boards on a Wall
What a great source of wood for all sorts of projects, you could make a garden table, raised beds for vegetables, standard planters https://www.1001pallets.com/2018/03/simple-attractive-planter-made-pallets/