The preferred file format for artwork is a vector file, preferably an .eps or .ai (illustrator) file. These vector formats ensure that shapes, sizes, and colours remain true to their original state. These graphics can be fluidly scaled to large sizes without any quality loss.
Files to avoid (jpg, tiff, png)
Raster graphics, such as .gif and .jpeg consist of an arrangement of pixels of various colours that form an image. When enlarged, these can turn blurry due to poor quality or insufficient resolution.