(ok first of all this makes me so happy that you’d wanna ask lil ole me for help on this ILY)

you could do:

• blogrates - this doesn’t have to be fandom centric at all or it could be if you wanted (make the highest option out of ten a character name (i’m guessing you’ve what i’m talking abt before but here’s a good example)) wow double parentheses i hate myself
• make me choose edits (if you’re into editing) - have them send you two characters/ships/etc. from your fandom and then you choose one of their options to make an edit on
• blog compliments/advice - this is a really nice and positive one and you basically get to rant abt how much you love everyone which is always a good time<3
• name playlists - create a 5 or 6 song playlist based on their name
• character/ship playlists - a fandom centric version of name playlists
• name aesthetics - here’s an example

or more blog/pages related celebrations:

• fandom family
• blogroll
• birthdays page 
• follow forever

ahh alright i’ll stop there but i really hope this helps! lmk if you have any other questions and congrats on 100 + good luck on your celebration<3