"Create a 3D model for a picture frame with a width of 3 cm, featuring small skulls placed side by side on the frame. The frame should be characterized by a dense concentration of details related to the skull motif, creating a uniform and subtle composition. Ensure that the skulls are evenly spaced, paying attention to proportions and symmetry for an aesthetically pleasing effect. Tailor the frame to accommodate a standard picture size while providing a clear and dominant representation of the skull motif. The final model should be prepared for 3D printing.