After creating the extrusion you can have a recessed area to receive the crest. This recessed area will keep the crest centred on the ring and it will also accentuate the shape of the crest.
The other process for creating the crest is to recess the design or carve the image into the ring. The will create what is called relief work and make it look like it was hand-engraved. Having the crest carved in the ring will give it an authentic feel much like signet rings from many years ago.
The next thing for you to decide is what shape the signet ring will be. There are several shapes available and the most popular are square, oval, cushion, octagon, and round. The shape that you choose should be based on the shape of your family crest. You will want to choose a ring shape that best matches the outside perimeter of the image. The main purpose for this is to prevent dead or unused space surrounding your crest. The other thing that you should consider putting in your setting is a comfort fit, especially if you are not used to wearing jewellery. This will make your ring easier to wear while providing a soft feel on the inside of it.