"Pixlr Express is a fun and powerful photo editor that lets you quickly crop, rotate, and fine-tune any picture, all in a completely ad-free experience." ---Google Play---
It is a great tool and it is very easy. You can easily create visual materials for your lessons anda save them. You don't need to download the programme. Just a website, here is the link. Creating collages with different layouts is the best part of Pixlr. Especially for the projects (Etwinning and Erasmus+), you need to have a look at it and use it.