I see what you mean. I like your selection of spells. What I was going for were spells that made a image or manipulated colors (Based on that, I should of put in Prismatic Spray). By the way, I never heard of the arcane-divine spell level rule.
If you changed the domain's name to "painting" it would be a better fitting i think 
It is not an "official" rule, but if you study the PH rules you'll find out that's the case in most places. Although i read it somewhere but i can't recall where.
Arcane magic is considered superior to divine magic. Therefore a divine version of an arcane spell with a +1 level is considered balanced. Consider the Anyspell domain spell:you trade a 6th level divine spell for a 5th level. There was a divine class in dragon which could cast divine as arcane but at a +1 spell level.
What i want to say is that it isn't an official ruling, but sense says that a domain with many key arcane spells on the same level is too good. Study the PH domains and you'll see.Also consider adding changing the "The DCs of disbelieving your illusions are increased by +2" with "The DCs of all your illusions with a visual part is increased by +2"
I see what you mean. I like your selection of spells. What I was going for were spells that made a image or manipulated colors (Based on that, I should of put in Prismatic Spray). By the way, I never heard of the arcane-divine spell level rule.