Hi,
VP does not maintain the original size of the imported images. You'll need to apply Scale effect to scale the images to the size you want.
The reason for that is simple: If we maintain the pixel size of the image on the output, you would have different result when you export to different resolutions. For example, a 100x100 picture will look bigger when you export 480p and smaller when you export to 720p.
Best Regards,