Sorry, here's what you will have to do to change the test under the intermediate image. If you don't have $template_display_media in your theme.php file, copy it from the sample>theme.php and paste it into yours.
// HTML template for intermediate image display
$template_display_media = <<<EOT
<tr>
<td align="center" class="display_media" nowrap="nowrap">
<table cellspacing="2" cellpadding="0" class="imageborder">
<tr>
<td align="center">
{IMAGE}
</td>
</tr>
</table>
</td></tr>
<tr><td>
<table width="100%" cellspacing="2" cellpadding="0" class="tableb">
<tr>
<td align="center">
{ADMIN_MENU}
</td>
</tr>
</table>
<!-- BEGIN img_desc -->
<table cellpadding="0" cellspacing="0" class="tableb" width="100%">
<!-- BEGIN title -->
<tr>
<td class="tableb"><center><b>
{TITLE}
</b></center></td>
</tr>
<!-- END title -->
<!-- BEGIN caption -->
<tr>
<td class="tableb"><center>
{CAPTION}
</center></td>
</tr>
<!-- END caption -->
</table>
<!-- END img_desc -->
</td>
</tr>
EOT;
For the title, find
<tr>
<td class="tableb"><center><b>
{TITLE}
</b></center></td>
</tr>
replace with
<tr>
<td class="tableb"><center><b><font size="14px">
{TITLE}
</font> </b></center></td>
</tr>
For the caption, find
<tr>
<td class="tableb"><center>
{CAPTION}
</center></td>
</tr>
replace with
<tr>
<td class="tableb"><center><font size="14px">
{CAPTION}
</font></center></td>
</tr>
You could also copy the tableb property in the style.css file and add a font size to the new property. Then change the tableb class for the above 2 sections with this new property. Something like
.tableb_intermed {
font-size: 14px;
padding-top: 3px;
padding-right: 10px;
padding-bottom: 3px;
padding-left: 10px;
}