Summary

I decided to make the hollow Celtic Skull into a LED necklace! I also did a single-skull version by gluing in some glass eyes purchased on Aliexpress. I created a flat spot inside to which you can glue an 18650 battery holder. Some self-flashing LEDs and a small slide switch are the parts I used for the 5-skull necklace.
You can change the model (remove the support bases if you want) by editing the model on Tinkercad

Print Settings

Rafts:

                                            <p class="detail-setting supports"><strong>Supports: </strong>                     <div><p>Yes</p></div></p>                                                                                <p class="detail-setting resolution"><strong>Resolution: </strong>                     <div><p>.2mm</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>25%</p></div></p>                                                        <br>                        <p class="detail-setting notes"><strong>Notes: </strong>                    </p><div><p>Printed with a wide brim with zero distance between brim and model. This helped with bed adhesion.</p></div>

Celtic Skull Necklace