@hubeny76: You can try these steps as a workaround.
sudo apt-get install imagemagick
temp=$(mktemp -d)
pushd "$temp"
mkdir 16x16
cp /usr/share/caja/icons/hicolor/64x64/emblems/emblems-insync* .
for emblem in $(ls *.png); do
convert "$emblem" -resize 16x16 16x16/"$emblem"
done
sudo cp 16x16/* /usr/share/icons/hicolor/16x16/emblems/
sudo gtk-update-icon-cache /usr/share/icons/hicolor
popd
rm -r "$temp"
This creates smaller versions of the check mark icons. You might need to restart caja for the changes to take effect. To restart caja, try running caja -q then caja ~/.