There are masses of really inspiring ideas on this site. I have clipped some of the ones that appeal to me under my board "Garden ideas". There are a few which relate to mushrooms, and all use things that have been recycled. I think you will find a few to get you started ... Have fun with the project, and don't forget to upload some pictures for us all to share!
Go to Pinterest. More ideas than a man could use in a lifetime. Click on a picture you like and it will enlarge. Click on the picture again and get the instructions of how it was made.