>> I am a bit behind with my March bingo card (9 prompts). There are still two prompts to go, so I will finish a bit late.<<

Late is totally okay here.

>>After finishing, I will create a new April card; maybe I will combine both April challenges, using the 'aesthetic' prompts and writing drabble fills.<<

What about making a card for each theme and then layering them? So take the B1 prompt from each card and combine them into one fill.