Crafting Tip: When brainstorming birthday card ideas using the collage technique with different media you may run into the problem of "filling out" the entire collage. To alleviate this issue, consider using patterned paper as the background of the collage to fill in any blank spaces ahead of time. Or use a repetitive signature piece of art of fill in the blanks, such as stars, colored buttons, hearts, happy faces, and other embellishments.
If you don't know too much about the person, but you know their birth date then you can still make a collage all about them! Consider birthday card ideas using their zodiac sign, precious stone for the month of their birthday, and if you know the year they were born you could also include their Chinese zodiac sign. If you still need some filler space, then find out some interesting facts related to their zodiac sign and print or write them on the front of the card. Everybody loves to read what they're all about and it could be a fun conversation piece so you can get to know the person better!