Strange icons artefact on app launcher
I have just installed Marshmallow launcher to get rid of that artefact. On the new launcher, the interface was new, no artefact. However, the artefact was still there on the stock launcher. Whenever I go to that launcher, that artefact was there.

Then after a few days, I just unintentionally go to stock launcher, then you know what, there was no artefact, the problem was solved!

Recently I have just found a way to get to the recovery option in my mobile. If I will ever face that artefact problem, then I will try to clean cache to see it solves or not as some of you said me to do this. Thanks guys!