Having this text:
If you want to match a filename with a very specific file extenstion, you can use something like this:
a slash followed by a digit followed by the letter 't' followed by two digits followed by '.jpg' at the end of the string
Or, if you really just want the filename (whatever is after the last slash with any file extension), then you can use this:
a slash followed by one or more non-slash characters at the end of the string
In your sample string of
http://img.oo.com.au/prod/CRWWBGFWG/1t44.jpg, both of these will match
/1t44.jpg. The first is obviously much more restrictive since it requires a specific format of the filename. The second matches any filename.