JoyPixels, formerly EmojiOne provides free and premium emoji, sticker, smiley and animation packs. They are currently in process of releasing JoyPixels 5.5 this month. Through out their releases from EmojiOne to JoyPixel 5.0, they have tried to add more details and make emojis more realistic.
In the image above you can see how they tend to add more details and try to lean toward a more real life like picture for those emojis. But I have to be honest, in some cases, I like their representative emojis better.