Sainer is a Polish painter and muralist, currently based in Gdynia, Poland. He is also one half of the artistic collaborative duo ETAM, along with Bezt.
I’m a little uncertain whether some of the murals shown above are collaborative.
They have a jaunty, sometimes cartoony style, but with definite attitude. Their large scale and presence on the sides of buildings give them a different character than they might have as stand-alone images.
In Sainer’s canvasses (images above, bottom four), he often takes a more refined and subtle approach (though not always).