No Hacking required for this.
Take the following Image and following BBCode:
Title: Schield
Tag: schield (or whatever you want)
Replacement:
HTML Code:
<table border="0" cellspacing="0" cellpadding="0">
<tr>
<td align="center" style="background-color: White; border: 1px solid Black; padding: 1px;"><normalfont>{param}</normalfont></td>
</tr>
<tr><td align="center">
<img src="absolut/path/to/your/image.gif" alt="" border="0">
</td></tr>
</table>
Use Option: No
Works on vB2 and vB3
If you want more than one Image use the Option tag and name the Images to schield1.gif etc. and use Filepath shield{option}.gif
Than call with [ schield=1]test[/shield]
I attached a Smilie.
Have fun.