After running librsvg 2.40.20 Yocto recipe, the libpixbufloader-svg.so is not available under usr/lib/gdk-pixbuf-2.0/2.10.0/loaders/ folder while it should be.
It's packaged in the librsvg-gtk subpackage.
OK, so librsvg-gtk must be added to the IMAGE_INSTALL even if librsvg is already added. That works, thanks.