Yes, by replacing the frame number with '%04d' or similar. For example, if you have a sequence of images called map.0001.tga, map.0002.tga etc., enter map.%04d.tga. The '04' is the number of digits in the frame number, and it will work with other numbers. The frame number is the same as the frame number being rendered; currently it's not possible to offset or scale the number to something different.
Matt