Well this would really depend upon your own preferences and the colour and pattern of your bathroom tiles. It is best to colour coordinate your tiles and your hand towels. For instance if your bathroom is in an earthy colour like brown then maybe you could pick up some light green towels to match or maybe even another slightly different but complimentary shade of brown.
As far as decorating the towels in your bathroom there's no limit to what you can do. First I suggest you buy some self coloured bathroom towels. Avoid towels with designs. Next you should try to decorate them with something that is both artistic and suitable for your bathroom. For example if you have an earth themed bathroom then you can try painting your towels with flowers (use fabric paints). If you know embroidery you could embroider attractive designs on the towels.
As far as decorating the towels in your bathroom there's no limit to what you can do. First I suggest you buy some self coloured bathroom towels. Avoid towels with designs. Next you should try to decorate them with something that is both artistic and suitable for your bathroom. For example if you have an earth themed bathroom then you can try painting your towels with flowers (use fabric paints). If you know embroidery you could embroider attractive designs on the towels.