spun edit text in circle on top of thumbnail

What I would do is set the default font properties for the thumbnails, then follow it with a rule that has any different properties for the non-thumbnails, like this:

/* This is the default styling for thumbnail titles */
.hentry span.thumbnail-title {
   display: table-cell;
   font-family: 'raleway', serif;
   font-style: normal;
   font-size: 16px;
}
/* This is the styling for thumbnail titles with no thumbnail image */
.hentry span.thumbnail-title.no-thumbnail {
   font-style: italic;
   font-size: 20px;
}

Adding the .no-thumbnail class makes the selector have a slightly higher specificity than the rule before it, so any thumbnails without an image will use the properties from the first rule, and any properties from the second rule that are in common with the first rule. That is, thumbnails with an image will only use the properties from the first rule, but thumbnails without an image will use the display and font-family properties from the first rule and the font-style and font-size properties from the second rule.