SpEd Forms supports custom logos provided they meet two requirements. First, the logo should be in .gif format. The second, is that its dimensions are 50×50. For best results please ensure a uniform shape and a transparent background. At this resolution, some detail can be lost, so it is best to avoid small text and fine details.
To add a custom logo please submit a support request from your SpEd Forms admin menu.
Pictured below is a simple example that meets both requirements.