You can recommend characters that have a chance to join the show! If you already signed up, you can still recommend a character. You can recommend multiple characters. You must sign up to recommend a character.
Here's a ruleset by Derpyunikitty here:
1. Recolors or minor changes on a existing BFDI contestant is OK.
2. Original OC's are allowed
3. Davids, even if based on a copyrighted character, are OK.
4. Objects that are something copyrighted (Ex. Nintendo Ds, iPhone, Pokemon, (But they have to at least have a david face or basis) etc.) but have object show eyes, mouths, and limbs are allowed.
5. Characters based on something outright, like Taylor Swift's head with object show limbs, a rip of John Cena's cap that is not it's own asset, or anything that is cringey are not allowed.
6. Non-Object characters are not allowed. Symbols (like Yin-Yang) and joke characters (like Big Orange Chicken) are allowed.
And one more I added.
7. Existing BFDI RCs are allowed, but object show characters are not.