In my illustration work, I try to be as accurate as possible. When illustrating real events that happened in a real place and time (or indeed, fictional events set in a real place and time) it makes sense to make the illustrations as close as possible to how it would really have been. And I love doing research about it - particularly the clothes.
So, when I was illustrating Daniel in the lions' den recently, I made sure to dress him with accurate Persian clothes and hairstyle for the time (really easy – there are so many ancient pictures to copy).
The thing is, though. How accurate is this really? I've given him grey hair, because he was in his eighties at the time. Actually, though, I've a feeling an important Persian official might have dyed his hair. But with a picture in this simple style, how else can I show he is old? And then of course, I've read somewhere (though not verified) that men at the time wore heavy makeup… That might look just a tiny bit odd to today's eyes!
So you have to compromise. If I were doing an educational book that could have info boxes explaining the pics, I would be more pedantic. But when a picture has to speak for itself, you have to not confuse people.
Of course, there are some times when it's OK to stretch the historical accuracy just a wee bit more…
Parts of King Darius are very accurate :-)