I'd add some lustrous velvets,probably patterned, to 2 Mongolians. Most of the Etsy shops I've used will send samples so you could test out the textures. https://www.etsy.com/listing/104078330/mary-mcdonald-vanderbilt-velvet-pillow?ref=shop_home_active_56
Also wondering if you would find Robert Allen's Glazed Linen an acceptable texture? Various colourways,here is one. https://www.etsy.com/listing/466828991/designer-fabric-metallic-brass-gold?ref=shop_home_active_50
Also,how do you want the formality of smooth silk? Like in an ikat or similar?
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