Here are some alternate buttons and scroll bars that provide a more simplified/basic look with flat monochrome panels and rounded corners. To install, simply place the folders in the zip below within the game's install folder (Program Files (x86)\Steam\SteamApps\common\Evochron Legacy for Steam or \sw3dg\EvochronLegacy for the direct download version).
These custom images will also provide you with a template from which to modify the buttons for your own designs using a complete image set.