I think Olga simply isn't receiving much fanart because her playable designs are overdesigned, tacky messes. Usually, Takeuchi misses with Stage 3 when designing Servants, but in Olga's case, he missed with all of her stafes because he went overboard when creating them. They all feel like poorly conceived Stage 3s. I think he wanted to do something akin to Lilith or Melt, but he missed that their designs mostly worked because they are simple and have pleasing color schemes.

You need multiple glances to understand what's going on with Olga's sprites, and even then, you will likely struggle to memorize all of her unnecessary details and comprehend what's going on with them.