A sharp pair of sturdy scissors and a steady hand will be required to produce a 'custom' pickguard from this quality material sheet. Finishing off the edges with a very fine emery paper will add to the finished item.
The 'tortoiseshell' sheet, once the protective front film and rear backing sheet is removed, is nicely translucent, letting the grain of the guitar top show through it (although probably not suitable for very dark coloured guitars - as the nice pattern, within the sheet, would not be seen).