Looks good. However, it seems to me that your GFX is smallish on scale. Idk if you're doing this on purpose. If so never mind.
On the helmet, it's fine to make a shine effect, but as in the picture... The light is coming from the side. On the rounded visor, a shine is located where the light is coming from. So, you wouldn't have that striped look you have made. Looking at different types of light sources and their effects on different surfaces/substances may help you.
Also, your hats look a little flat. Work on your depth a little bit. In addition to that, unless your light source is coming from the front, you shouldn't pillow shade. Aka: the yellow on the helmet. Using different light sources can completely change the look of your graphic.