If you want you can create an HTML table and then upload images into it and display it in your sidebar. It's not hard to do at all. Your limitation is of course the width of the sidebar in your theme > http://wpbtips.wordpress.com/2010/01/11/sidebar-width/
HTML tables are constructed of rows and cells. How many rows and how many cells is up to you.
* table means “start” the table.
* you can adjust numbers in border, cellspacing, and cellpadding; align center, right, or left
* headings in a table are defined with the <th> tag like this <th>Another Heading</th>
* body means start entering your contents into the table
* tr means start a table row
* td means put data, image or text
* repeat td as many times as you want cells across your table
* repeat the table rows (tr) as many times as you want
* for every < there is a > <something>
* for every < > start there must be a </> close
* </table> means close the table
Example
<table>
<tr>
<td>row 1, cell 1</td>
<td>row 1, cell 2</td>
<td>row 1, cell 3</td>
</tr>
<tr>
<td>row 2, cell 1</td>
<td>row 2, cell 2</td>
<td>row 2, cell 3</td>
</tr>
</table>