The diamond eyelet stitch is technically worked like the algerian eye stitch. Only, it works around a diamond outline, and carries more spokes (straight stitches) for a filled effect. Again, this can be used wonderfully over even weave cloth to create great textured fillings.

I will be working within a diamond shaped area to illustrate this stitch. This illustration shows working the straight stitches from the outside to the centre. You can work the straight stitches from the centre too.

diamond_eyelet_stitch_1      diamond_eyelet_stitch_2
Fig 1: Start by bringing up the needle from a corner of the diamond shape, point A. Take the needle in through the centre, that is, point B. Then, bring the needle out from C and again in through B, as shown.     Fig 2: Keep up with this procedure to fill the entire diamond shape. Keep the number of straight stitches even, atleast twelve.  
diamond_eyelet_stitch_3   Fig 3: A finished diamond eyelet looks like this.