Hello moirae, First of all I agree with @alexandre-mattosb the pose is just gorgeous. The clothing fits really well and I appreciate the simplicity of the design not to mention how well the tail complements the gesture.
Ok I took the time to do a bit of an over-paint (hope thats ok with you). You mentioned how the character doesn't seem to pop. The background is not the issue here. The issue is the lack of contrast, especially on the character, although the clothing could use a bit more as well.
Here I took out all the color so you can see what I mean. The darkest value on the character is about half of the value scale. Another thing is that you have way too many light areas and too many pure white or almost white highlights. Highlights are like the cherry on top they can give that extra pop to your painting but you need more variety in your values to make the highlight stand out.
Some areas of the body are too tight when pressed together, like the armpits, the crotch etc. These part do not allow much light to pass so you can push the dark values there ( occlusion shadow).
Based on this I put some notes and did some adjustments in greyscales. Keep in mind this is very rough but I hope it helps explain what I said.
Dont be afraid to put some darks in your images it really helps in making them feel more three dimentional. With this all that is left is to put your colors back on it using a duplicate layer in color mode.
The colors dont match exatly but as I said earlier its a very rough fix.
I do hope I was able to help in some way dont hesitate in letting me know if you didnt understand something. Keep Up the great work see you around