Looks good, but I have a few small suggestions.
1. Try putting the image on a transparent background instead of white. Make sure to save in PNG format though; GIF doesn't support alpha-transparency (meaning, with GIF, each pixel must be either fully opaque or fully transparent -- with PNG you can use partial transparency, which is good for the shadow effect and for smoothing around the edge of the image).
This adds the problem, though, that Internet Explorer doesn't handle PNG properly (it ignores transparency and puts the image on a solid background). So Firefox and other users will see your image as intended, while IE users will see it as it is now.
You can use GIF, but then you lose the alpha-transparency. The edge of the image may become jaggy, and the shadow will look like crap (on a white background it will look fine, but people on this board all use different themes -- and I don't think any of them have white backgrounds

).
2. The text is jaggy. You should be able to adjust anti-aliasing somewhere; unfortunately, I use Photoshop, so I can't tell you how to do it on GIMP. For Photoshop it's along with font size, style, etc. :-\ It's probably in a similar place for GIMP.
Have fun
Those who will remember, will speak fondly of the warm morning breeze.