The following regexp, should be placed first in the convert_wiki_text block:

<pre>
text = text.gsub(/\[\[Image\(([a-zA-Z]+\:(\d+\:)?)?([^\)^,]+)[^\)]*\)\]\]/, '!\3!')
</pre>

The following test cases:

puts convert_wiki_text("&#91;&#91;Image(myimage1.png)&#93;&#93;")
puts convert_wiki_text("&#91;&#91;Image(wiki:myimage2.png)&#93;&#93;")
puts convert_wiki_text("&#91;&#91;Image(ticket:1:myimage3.png)&#93;&#93;")
puts convert_wiki_text("&#91;&#91;Image(myimage4.png, 120px)&#93;&#93;")
puts convert_wiki_text("&#91;&#91;Image(myimage5.png, align=right)&#93;&#93;")

Will then output:
<pre>
!myimage1.png!
!myimage2.png!
!myimage3.png!
!myimage4.png!
!myimage5.png!
</pre>

I think the only supported extended Image attribute supported by Redmine is align=right, which could have been converted to:
<pre>!>myimage5.png!</pre>
...but it's probably pretty rare, and would make the already complex regexp almost unreadable.
--------------------------------------------------------------------------------
Any news on this?
Is anyone able to reproduce this with the current trunk?
--------------------------------------------------------------------------------