Standard tiaras are made from twisted metal and are either decorated with crystals and beads, diamante, or for the less money conscious, real jewels and gemstones can be used for a truly exclusive look. Tiaras tend to rise to a point at the front, where most of the decorative work is and has a gap in the metal work at the back so that it can accommodate veils and intricate hairstyles,
Crowns can either be made in exactly the same way as the tiaras mentioned above, however there is no break in the metal work at the back to form a circular headpiece to sit atop the head. Alternatively, instead of twisted metal and crystals it can be made from solid metal. If a veil is to be worn it can be placed at the rear of the crown. Hairstyles suiting crowns are either sleek styles, either up or down, tousled curls left loose or a high bun (either sleek or curly) around which the crown can sit.
A final head piece option is one of flowers, either dried, fresh or silk. Either an arrangement attached to a comb-style hair slide or made in to a floral ring to wearing a similar way to a crown or a more contemporary option is to attach flowers (either in small clusters or individually) to hair slides and dot into place as part of your selected style. These can be combined with crystals or feathers for a contemporary look. Or to capture that beach babe feel use a single large flower which matches your wedding colour scheme, Gerbera for example, pinned in to your locks.
As far as Jewellery goes, you need to get something which complements your engagement ring, tiara and dress (colour and neckline). Realistically you are probably looking for a necklace and earrings, possibly a bracelet.
If the neckline of your dress is on the low side a pendant style necklace will break up the space and add detail to a bare neckline. Higher necklines might be better suited to a chocker style. A very high neckline such as high collar or slash neck could go with a longer pendant or without anything at all.