I get:
$ echo -e \"D\"{a,b,c}\".jpg\\n\" Da.jpg Db.jpg Dc.jpg
Note: The extra spaces before Db and Dc on the 2nd and 3rd line of the outp
The easiest and cleanest solution is to add a backspace to the front of each line:
echo -e -n "\bD"{a,b,c}".jpg\n"
This produces the desired output.