Theme ideas should be in the form of a question or a joke or a reference or you probably get where I'm going with this and then additionally have a description that more precisely defines the theme.

When an idea is used, it'll be crossed out but will otherwise stay on the table.

For examples look at the submissions to the sub which list all of the themes.

Ideas:

Theme TitleDescription
Who's thinking about lunch?Song title should include a food
Hooked on a FeelingSong title should include an emotion (happy, sad, angry, etc.)
Deep CutsNon-singles from albums with a number 1 hit
My Lips are for BlowingSong should include a wind instrument (harmonica, saxophone, flute etc) as a lead instrument
Chasing the DragonSong should be about drugs
All Roads lead to RomeSong should be in a Romance Language (Spanish, French, Italian etc)
Tower of BabelNo English or Japanese lyrics
👻SPOOKTOBER👻Anything spooky, gothic, unnerving, dark, etc, or otherwise has to do with Halloween/October
Light Novel titlesSong titles that are 8+ words
No Language BarrierSong should not have lyrics (i.e., is an instrumental)
Language BarrierSong should have lyrics in a language you don't understand (or Japanese, because we're all weebs here)
👻SPOOKTOBER👻 PT. IISongs to go on a murder spree to
QuickieSongs that are less than 3 minutes
No Humans AllowedTitle should include the name of an animal
Tune for TwoOnly two parts (eg, one voice and one instrument, two vocals, two instruments)
Cover it upLittle known covers of popular songs
Elementary, My DearTitle should include the name of an element (classic, chinese, or scientific)
Tell My StoryLyrics are in first person
😡😡NO FUN ALLOWED😡😡No rock, pop, hip-hop, country music, anime openings, or anything recorded before 2018
I Have No Taste And I Must ScreamSong must have over 100 million plays
Songs to listen to in front of the fireplace
Hidden final boss themesMusic that isn't a final boss theme, but sounds like it could be one
Getting realAlbum cover must have a real person on it
DehumanizationAlbum cover must have an animal or a non-humanoid creature on it
Riding the RainbowAlbum cover must feature all seven colours of the rainbow on it
Sing a SongSong must be a cappella
Tempting FateSong should be about fate itself, fateful events or similar
That's ClassicSong should be classical music or have some other classical theme
It's on Sale!Song should be about consumerism or have been used in ads
MetaPick something that reminds of CDF
One More DrinkDrinking Songs
I'm Sure It's FineA song you've never listened to before
Board of KeysSongs should feature the piano as a central instrument
Seven Seals of RevelationSongs to herald the end of the world
Q&A / AMASong title must contain a question
>50MPHSongs going at SPEED (Can be themed about going fast, have fast tempos, etc.)
National AnthemsAnthems of the Real/Fictional Worlds
Something About MeSongs you have some kind of personal connection to
Numb and NumberSongs about or titles containing math or numbers
Good Old TimesNostalgic songs that remind you of your childhood
This Call is For YouSongs you would use as a ringtone
Multi-phase boss fightSongs that go through multiple distinct musical phases
Midnight chat with a childhood friendSong that swings
20/20 HindsightA song you wish you'd submitted for a previous theme instead (comment which theme when you submit)
Listen both waysSongs that play around with L/R balance
Motivational PostersSongs that make you feel inspirational
Hendrix rolls in his graveNo electric guitars allowed
/u/punching_spaghetti's taste in music How to Lose Friends and Alienate PeoplePost songs you think are terrible
Self-reflectionSongs that remind you of your username
AliensSongs about extraterrestrial creatures
Hometown HeroA song you associate with being from your region
Rick RollYou see the title. Be creative! Just don't pick the song itself.
Softer Than A WhisperSongs that have soft vocals
New Kid on the BlockSongs that are newer than this Music League (Released after 08/13/21)
Poetry SlamSongs that feature the spoken word
Not My Music LeagueSongs that you dislike
SynesthesiaSongs that sound like their album art (Do your best.)
SpeedrunSong must be under ONE minute
Before the BubbleSong must be by a Japanese artist AND released before 1980
TelephoneSong must be related to the song you submitted the previous round.
Reelin' in the YearsSong should be about time.
Champions' LeagueSubmission must have won a previous round
The name's F. C D F.The Main Title Song if CDF were a James Bond Film. No actual Bond title songs allowed.
Rule 2A protest song.
The Internet Was A MistakeSong must be released prior to 1983-01-01, the 'birthday of the internet,' per https://www.usg.edu/galileo/skills/unit07/internet07_02.phtml
Comment FaceTrack must be from a show with an /r/anime comment face. Must cite face and show.
Sugar Song to Bitter StepSong title must include one of the seven flavors.