Yes - provided that the original wallpaper is paper based (no vinyl) and glued evenly to the wall, without bubbles or loose bits.
If your wall is covered with fiberglass wallpaper (glasvlies/glasweefsel/Glasfaser Tapeten) you can also apply Inke's designs over it, but be aware that the embossing of the fiberglass will show through the silhouette (better not use the 074 (silver) or 075 (gold) wallpaper).
