I like simple designs, designs that seem elegant to me, even some older designs. I would suggest finding designs that you like and either scale them up or down so you can clone them, or take styling cues from some and apply to the parts that you have. I think the fin shape provides most of the style to a simple rocket, the length, nose cone shape, and paint provides the rest.
Need more inspiration? Flip through all the catalogs you can find, both old ones and new ones. Anything that catches your eye think about whether you would like to clone it or take parts of its design and combine with other ideas.
Still need more? I like fin shapes like the standard Nike booster, the nonsymmetric shape of the CherokeeD, Swept trapezoidal fins like the Army Hawk, pick one of those designs and build with it.
