Copying only files without a special string in filename
As find's -name does not support regular expressions you will have to explicitly define the four cases

find /source/ \
    -not -name '*[0-9][0-9][0-9]x[0-9][0-9][0-9]*'           -and \
    -not -name '*[0-9][0-9][0-9][0-9]x[0-9][0-9][0-9]*'      -and \
    -not -name '*[0-9][0-9][0-9]x[0-9][0-9][0-9][0-9]*'      -and \
    -not -name '*[0-9][0-9][0-9][0-9]x[0-9][0-9][0-9][0-9]*' \
    -exec cp {} /destination/ \;