Si, el content manager ya incluye un importer, ahora bien no se si tiene algun tipo de limitacion.
Effect Class .fx
Model Class .fbx, .x
SpriteFont Class .bmp, .spritefont, .dds, .dib, .hdr, .jpg, .pfm, .png, .ppm, and .tga
Texture Class, Texture2D Class .bmp, .dds, .dib, .hdr, .jpg, .pfm, .png, .ppm, and .tga
TextureCube Class .dds
Effect Class .fx
Model Class .fbx, .x
SpriteFont Class .bmp, .spritefont, .dds, .dib, .hdr, .jpg, .pfm, .png, .ppm, and .tga
Texture Class, Texture2D Class .bmp, .dds, .dib, .hdr, .jpg, .pfm, .png, .ppm, and .tga
TextureCube Class .dds