Lovely colours!! I agree with 'pluckyfilly' about it being a little too much to the left - but as for the background, it's quite easy to replace if you have a post processing programme. I use Photoshop Elements 9 but there are free ones you can download from the internet (Gimp is one, but there are others).
With this, because it's quite a simple shape I would 'Select' the flower (which would stop that being changed in any way), then (using the 'Clone' tool) I would choose the grassy background and move the tool over the fingers. This would replace fingers with grass. After that, I might give the image a little more canvas (space) on the left and fill that with grass. In this way you can put your flower on the 'third'. There are a few 'soft' areas on the flower. This can be cured by using the 'Sharpen' tool, just running it over the soft areas.
I really do like the yellow against the green though, quite eye catching!