Please note that the Synfig SIF format is subject to change so this may not always work.
Synfig Studio currently only supports importing bitmap images or its own vector image format. This can be annoying, especially since many use Inkscape for drawing. There are a couple of converters that might be useful:
SVG: A XSLT transform for converting SVG files directly to SIF format. Also there is a C program that converts SVG to SIF files directly.
GIMP: A GIMP plugin for converting GIMP images to the SIF format.
Synfig currently only supports exporting bitmap images or video formats. This can be annoying, for artists who like to work with multiple media and multiple software programs. There is a converter that might be useful:
SVG: A XSLT transform for converting SIF files directly to SVG format.