I know, no one REALLY cares, but …
Alpha testing comes before Beta testing. In the classic waterfall development model a project reaches Alpha when all features are present, though they may not all be functional. By contrast, Beta is usually defined as all features present and functional and all bugs addressed between build versions.
That said, I agree with Savage about panel graphics not being necessary for testing the functionality of your modules. The only thing you lose is testing of the panel graphic itself. Misalignment, typos, legibility… that sort of thing. Use blank panels, aluminum sheet, plastic, whatever works. Test units don’t need to be pretty, just functional.