If you just want space:
span.intent-meta a.in-reply-to, a.retweet, a.favorite { padding-right: 5px; }
If you want a background image (e.g. as at https://bioneural.net) from:
https://dev.twitter.com/docs/image-resources
Then use these 3 CSS rules in your stylesheet:
span.intent-meta a.in-reply-to { display: inline; padding: 2px 0 2px 20px; background: url(‘images/reply.png’) left center no-repeat; padding-right: 5px; }
span.intent-meta a.retweet { display: inline; padding: 2px 0 2px 20px; background: url(‘images/retweet.png’) left center no-repeat; padding-right: 5px; }
span.intent-meta a.favorite { display: inline; padding: 2px 0 2px 20px; background: url(‘images/favorite.png’) left center no-repeat; padding-right: 5px; }