Style Cues
Some of the best style cues that automatically produce good results in very short prompts include the following: emoji, emoticon, emojified, icon, sticker, line art, cartoon, pictogram, ideogram, logo.
Some other useful style modifiers include: symmetrical, minimalist, 3d render, modern flat design, isometric perspective, neon.
If you end up with black and white art, but want color, the modifiers colorful or full color will usually correct that. Other optional cues could be to name a color or color theme in general, but mentions of color sometimes cause the background to take on those colors unless you explicitly say, “white background”.
With the standard Dalle-E 2.0 model available via Labs, combining multiple style cues may yield better results than using only one, so feel free to mix and match them as you create your emojis. Remember to keep a simple subject that will “read” immediately for your emojis.