Without using the .htaccess file you described, use your Browser and go to the images dir. of your site. Do you see a blank page or a listing of sub-directories and files.

Could be, if your Hoster is smart, that they have already disabled directory indexing; which is what the -Indexes means. If so, you do not need to use it any .htaccess file and things might work properly by just using:
Options +FollowSymLinks

If you cannot use the Options directive for anything, then you could ask your Hoster why that is so. Could be they've got some Server-wide security setup in place and can suggest an alternative directive to use.