I left them under /com/eteks/sweethome3d/io/resources/openwooddoor/images/.

There is a file called textures.txt with the following content in /com/eteks/sweethome3d/io/resources/openwooddoor/:
<../images/texture0.jpg> <../images/texture0.jpg>
<../images/texture1.jpg> <../images/texture1.jpg>