I’d like the option of having the total number of tickets/spaces available along with how many are left on the event, so that people can see if they need to sign up soon.
For example:
5 out of 15 spaces remaining.
or
10 out of 15 tickets sold
or something?
I get emails ALL THE TIME from people saying, “How many spots do you have left?” so it would cut down on admin time.

AlphaSmith
WP EO Pro already has this functionality.
See these codex pages :
http://codex.wp-event-organiser.com/function-eo_get_event_capacity.html
http://codex.wp-event-organiser.com/function-eo_get_remaining_tickets_count.html
Below is an example of the code that may work for your situation:
$remaining = eo_get_remaining_tickets_count( get_the_ID() );
$capacity = eo_get_event_capacity( get_the_ID() );
if( $remaining > ($capacity/2) ){
printf( '%d out of %d tickets sold.', $capacity-$remaining, $remaining );
}elseif( $remaining > ($capacity/4) ){
printf( 'Hurry, only %d tickets remaining', $remaining );
}elseif( $remaining == 1 ){
echo 'Only one ticket remaining!';
}else{
echo 'Sorry, there are not tickets available';
}

Dario