Designs can be from all the different kind of files : scan, drawing, pictures, vector, logo, mixed composition ( ex : drawing + pictures ... ).
By the way, most of classical files format are alright :
- bitmap files as .jpg .png .psd .tif .eps photoshop etc ...
- vector files as .ai and .eps
To begin with good basis, use the downloadable skateboard templates >here<
These are real size templates (82 x 21 cm) high resolution (300dpi) and can be printed with mo loss of quality.