I posted about sticker stories a while ago on my blog here. When I have grade 2s, we start sticker stories in the fall. With my grade ones, I don't introduce them until the spring.
The biggest challenge is finding stickers that match the French vocabulary that they know! I have a lot of cheap Dollarama stickers but they're obscure things. The best stickers I've found are from Michaels. They are about the same price as the pads from Dollarama, but they are ADORABLE.
We do them together on chart paper for a few times before I let them do it on their own in their journals. You can see an example of one we did last week above. We did another one with Elsa (from Frozen) and Spiderman, which they loved!
We set a limit of 4 stickers per journal page/story. Otherwise things get quickly out of control!!! They choose their stickers, draw details around them, and then write a story about the scene! They LOVE stickers and it's great motivation to do some writing :)