Words for the "essential character" of each sense organ?
As parallels for your 'flavour' and 'timbre,'
for touch tactile adj., tactility n. Critics describe a sculpture that visitors want to stroke as 'tactile.' for smell aromatic adj., aroma n. but 'Quelle est cette odour agréable,...?' in Wiki is translated fragrance.
I think sight is too complicated. The picturesque movement now seems dated. Pictorial is lame. Effulgence is a bit OTT, bright and making an impact, it covers colour and brightness but not form or interest.