There is often some confusion between Austrian blinds and festoon blinds and curtains. For the purposes of these projects, Austrian blinds are that which have some fullness in the width, causing the lower edge to fall in deep scallops. The depth of these scallops is determined by the amount of fullness across the width and the overlong allowance. They are made to pull up above the window; they may drop to the floor or finish just below the sill, but as they are overlong the bottom is heavy and the scalloped edge is a feature.
Any fabric can be used to make them up, from a light sheer to a heavy bombazine or worsted wool. In general, a lighter fabric will require more fullness than a heavier one. Something that doesn’t crease is the better choice–I’ve found that the both matka and tussar silks work well, they are soft to handle, gather well and seem to hang out free of creases.