When Arjuna left his family connections, he went to the Himalayas. The picture may be shown of Arjuna going step by step to the Himalayas; Yes, occasionally devotees may be pictured with full head of hair instead of sikha. You should use your own discretion; the garb can be Vedic or "American." There is no harm. Dress has nothing to do with the soul; Foods in the mode of passion are those that are very rich, such as kachori, halava, rasgulah, etc. They are also foods too much spicy. All this is described there in Bhagavad-gita.
Vidura looks like a human being; "self-same body" means looking like material body. Any devotee always is in a spiritual body although it may appear material; Smoke is smoke; When Krishna says unto me, he means unto "me." So he should not be pictured with Radharani,* Why a snake? Being entangled in the qualities of material nature is very subtle, so why a snake?
I am so glad to hear that the devotees are appreciating that everything belongs to Krishna. That attitude is very nice and should be maintained. Actually it is a fact. By illusion only we think things belong to someone else. And if the painters are new, certainly they should be given instruction. They should be helped in every way.