General clues:

Many of the not yet found characters are from the 1980s Superboy series. Batman (1960s), Wonder Woman (1970s). Lois & Clark, Constantine, The Flash (1990 series) also account for a number of not yet found characters. Don't forget that you can ask me if a character is from a particular show, movie, etc using 20 questions.

At least two characters from commercials are from a live show, thus only qualifying because there was a commercial for the live show.

One character is from a well known episode of a series that isn't normally connected with DC characters.

Quite a number of foreign uses of characters are on the board. At least one (related to a video game) probably was authorized by DC or at least Warner but many probably weren't.

Some remaining characters from the same non-SNL skit.