LeBlanc's Classic Model
When I see LeBlanc's splash art then read her lore, I see two very different people. When I look at her splash art, I see a power hungry enchantress who uses both magic and seduction to get what she wants. When I read her lore, I see in my head a mysterious entity with magical capabilities and can deceive you into believing anything she wants you to. These are two very different champions.
It's not her being sexually attractive or pretty that keeps me from seeing her as she is portrayed in the lore, by all means keep her pretty, it's really just what she wears. With the gem staff and the ornate golden circlet, not to mention the golden bracelets and over the top cape, it just gives off an aristocratic/power look that doesn't really mesh with her lore. In the lore I imagine her favoring silver or other similar colored metallic jewelry over gold, and she's constantly referred to as the "pale woman" which causes me to see her in more somber clothing, with grays and faded blacks. Maybe give her a hood with the whole Darth Sidius look, where her eyes are constantly cloaked in darkness. For her staff, I see it made of obsidian with an ornate design and at the top it's carved to look like a rose.
This is only for her classic skin so it's not like Riot would have to rework the rest of her skins..