Is it possible to make magento use the image of a simple attached product on configurable products if one exists?
Aka, chose a red bike from the config options and the red image loads, however if no image is attached for the red bike, then show default configurable image
As already stated by Amasty in the comments, this feature is called "color swatches" and there are many extensions out there which offer this functionality - though most of them are not for free:
The guys at Inchoo also wrote an article which explains how to implement it yourself.
You should definitely have a look at the extension Easylife_Switcher, which is for free and developed by the one and only Marius.
