I finally had a break and so spent some more time on this.  I recommend to anyone working in CSS to download the IE Developer Toolbar to confirm stylesheet changes.  I had been using it to troubleshoot but had yet to explore the "matches" menu option which shows hits on stylesheet entries for the current page.  I knew from traversing the DOM that the id of the control not rendering was:

dnn_IconBar.ascx_imgVisibility which I tagged in my stylesheet as IMG#dnn_IconBar.ascx_imgVisibility

Matches showed that this CSS entry received no hits.  On further inspection I saw that IE had rendered the name of the stylesheet tag:

IMG.ascx_imgVisibility#dnn_IconBar

I am now under the assumption that the (.)period in the ID of the tag is somehow causing IE to choke on the stylesheet.  When I get a bit more time I will edit the ascx file and rename the id of the control to see if in fact this is the problem.  If so...I will post and propose a change.  I also recommend not using (.)periods in id's.

The dot may be legal.  But I changed the iconbar.ascx.vb file so that the line 137 reads:

From - Me.ID = "IconBar.ascx"
To -      Me.ID = "IconBar"

Once I did that it picked up the styles in my stylesheet.  Again I used the IE developer toolbar's match count option on the stylesheet and now the styles are coming up with one hit each.  I had to add 2 entries to get it to work:

a#dnn_IconBar_cmdVisibility
{
width: 12px;
height: 15px;
}

img#dnn_IconBar_imgVisibility
{
width: 12px;
height: 15px;
}

It is not unusual for some browser implementations to choke on images without width and height.  I might also mention my renaming brought it in line with the standard naming convention used in DNN skins which don't regard a (.)period on tag id.  The fix works across IE Mozilla Netscape Safari and Opera.  Everything now renders within a 1 or 2 pixels of each other.

One more mention on the Control Panel and liquid CSS.  Set the width on the container DIV you create to 99% to fix stability problems with it bumping the screen width (and producing a scroll bar) when appearing in some browsers. 

At some point I am going to nail the control panel in pure CSS.