I agree with the others. The scoring on the gallery is really a poor way to judge your work. Considering the quality of work on this site, getting 9s and 10s is really really tough. And often I find the 1-10 scoring isn't sensitive enough. Maybe I think something deserves an 8.5... well, my only options are voting 8 or 9, so what do I do? When you've submitted several pieces you can start to look at trends... are you getting mid range scores of 5-7? Are you moving towards the higher ranges of 8-10?
But yes, I agree the score is too low. I'd rate this somewhere between 6 and 7. You're painting is very clean and you've done some nice free hand with the rose and the checkerboard pattern. What I think is hurting your score is the low contrast on your shading. Work on adding some stronger shadows and highlights, along with smooth blending between them and this will easily jump up into the 7's and perhaps into the 8 range as well if you keep up with the freehand. You can do other things like weathering (paint chipping, rust, dirt, oil stains, etc) which will help move towards those 8s, but the contrast is what I'd focus on first. Take a look around the gallery at some of the recent 8-10 rated work. Pay attention to how dramatic the highlights and shadows are.
If you do want to share your work, consider starting up a work in progress thread. It's a great way to get feedback (much better than the gallery in my opinion) and you can avoid the harsh scoring that comes with posting to the main gallery.