Cotton is not the only material used in batik. Batik can also be done on a variety of fabrics like silk, wool, velvet, felt or linen and is also very effective on papers. Batik can even be done on leather, wood or ceramics. Other forms of dye resist can be used, for example flour, cassava or rice paste, even masking tape. The wax can be applied using a variety of brushes, tools, stamps and sponges to achieve different effects.
As well as brushing on dyes you can also apply bleach, which can remove dye but also create amazing colours, difficult to reproduce with dye alone.
In summary, there are no limits to the exciting effects which can be achieved – I have spent half a lifetime experimenting!