If you want do something more fancy and really separate code from normal text to look more professional, there is another option:
You can use any standard HTML editor, such as free BlueGriffon, or even use MS-Word (save as web page).
Then paste your code into a table, using background color, table header, etc.
When done, select the content in Wysiwyg mode and simply copy it into the forum editor using the standard view.
The forum editor is buggy, but you can experiment with it and create your own document template for code inserts.
I can't see externally hosted image sites from work (yes we're 'crippled' in that respect too). However I do have Terminal font if I don't look through Word, as it's certainly available as a choice in my installation of TOAD, however I actually use Lucida Console in that. I've used Courier New before and not found that an issue myself... like I say I guess I'm used to seeing the differences. Personal preference I guess.
As for our organisation crippling systems, it's a necessary thing due to security requirements and for maintenance purposes (there are over 4,000 members of staff using hundreds of different applications so ensuring consistent client configurations is important). Being in IT myself, my computer isn't as crippled as a standard member of staff. At least I have free access to the hard drive and to be able to install (approved) software. Web browsing however, is restricted and the browser is via a citrix setup, so I have no control over the software on the citrix side. It works though.
Terminal looks like bold shouting on my setup, I've only been using it because I forgot about the courier fixed thing. I think I've even previously asked for Lucinda. The way people randomly change fonts at my work sometimes makes me chuckle, as I'm surprised when I start touch typing responses and then look at what is there. Thanks all for an interesting thread, special thanks to Dude for these explanations.
Terminal is indeed a ugly font. It resembles the font that was used for MSDOS on old analog CRT screens and was introduced with MS-Windows. Courier uses the typeface of an old fashioned typewriter. Both, Terminal and Courier are monospaced fonts, where all letters including the space have a fixed width (for those who don't know). Courier might be ok for SQL and data in pivot tables, but its known to have a potential risk of a letter mix-up for code and system administration. For instance, command -Il -O1, will be confusing for most people. Between Courier and Terminal, I would choose Terminal. However, I think it would be the best option if the forum web page could embed a good font for code so that everyone can see the same result regardless of system installation.
FWIW, here is a little comparison of monospaced fonts: http://i.imgur.com/rR0AKfl.jpg
I created this list on my own computer. I do not have the Terminal font, but Terminus (Linux console) seems very similar. My preferred choice is Menlo (Mac Terminal), followed by Meslo (GPL). Many people seem to prefer Consolas, which comes with MS Windows/Office. My second choice was Andale Mono.