you can use any fabrics you like- it's your project.
one year i made 3 underground railroad quilts- one done in 1800's reproduction fabs,
one done in 30's fabrics and white...
and one done in batiks....
all 3 are beautiful!
when i work with 1800 repro's at times i need to add other fabrics- i try to stay in the same color range/or i stick with adding solids instead of prints that look too modern- if i find a print that looks from the right era i use it.