Actually, this is Solaire of Astora, a character from Dark Souls (the first installment of the Souls series, an insanely popular action RPG game series with a very punishing difficulty level). Shovel Knight is a good guess though, since he does look a lot like one in this picture, but 'Praise the Sun' is a direct reference to Solaire, which has become a meme of sorts.
In the game, you first meet Solaire standing over a bridge, gazing at the sun. When you talk to him, he states his love for the sun, as if it were his God, and gives the player a white soapstone, which enables cooperative play in the game. As such, players got irrationally in love with his character, which created a lot of catchphrases for Souls fans which are related to Solaire. For example:
- 'Jolly Cooperation', as Solaire sais this in the game... somewhere (I dunno) when you summon him to help at a boss battle. - 'Praise the Sun', a line dedicated to his love for the sun. This one is often said while keeping the legs touched and spreading the arms in the air, creating a Y-pose (this pose is an emote you can get from Solaire as well). - many more, I dunno, I like the games, but I'm not THAT into 'em...
That Y-pose is what the picture shows: Solaire, in his knight outfit, praising the sun. So there you have it, a massive explanation noone asked for. ... You're welcome.