Duetto

Dude, you don't need a background. The action is right here.
I like the light creeping into your shadows there; the blue and red meeting in the middle..
So, you drew the ring in plain sight. I like how it draws attention and adds more meaning to the picture.
The sparkles are very nice, really smack you in the face and stuff.. The fingers are real delicate and I like how you've arranged them; Yuuri's on Viktor's neck and shoulder, and Viktor's on Yuuri's wrist. Those hands in particular.
I also like the folds in their costumes, the way you've drawn them large and sparingly makes the fabric look heavy and as if made with more care.
To better hide the background, if you're so concerned about it, you might've added some light reflecting off their bodies. This could bring more attention to the centre foreground of a picture as well.
The blue is so pretty, it really pulls me in. Then I see that ring. The colour playing between these elements creates a friction that leads me up to Viktor's eyes, I think this movement works well. 
You've coloured the silver bands quite nicely, with their reflective light and shading in general. The two in the middle work well together with Yuuri's arm: This shape helps with movement as well.
Yuuri's tail is so floaty, the way you've ignored it makes it appear simple and as if it really is caught in space. The contrast between it and the background creates a believable distance and it brings the figures out more.
Well done.