The PTO has waived a requirement that drawings filed through the Trademark Electronic Application System (TEAS) have a length and width of no less than 250 pixels and no more than 944 pixels.
According to the rules, submitted images must be in .jpg format having at between 300 and 350 dots per inch. All lines must be clean, sharp and solid, not fine or crowded, and produced a high quality image when copied.
Source: 69 FR 59810.