A cool tool to use in order to make digital posters is Glogster. The premium account I've had for this year (2109-20) allows me to create projects and assign them to my students. Here's a Glog I've recently updated and assigned to two of my EFL classes (https://edu.glogster.com/glog/the-three-billy-goats-gruff/1k7aapbi8sr) :
