A common reason for this is that you are replying to a Plain Text message and Plain Text messages simply cannot hold any formatting or embedded object such as pictures.
Quick workaround
A quick workaround is to change the message format from Plain Text to HTML and then to reinsert your signature.
Customize Plain Text signature
While the above workaround is effective, it is not considered “nice” to change the message format from Plain Text to HTML when replying as there might be technical reasons for the sender to send in Plain Text to begin with. A common reason is that the sender is using a mobile device which only supports Plain Text and thus your picture won’t be seen anyway.
If your picture contains crucial information which you really want in your signature (for instance when you use a picture of your business card as signature or a company logo instead of typing the company name), you can customize your Plain Text version of you signature to include that information in a typed form instead of as a picture.
To edit only your Plain Text version of your signature you can do the following;
- Hold CTRL when clicking on the Signatures… button;
- Outlook 2007 and previous
Tools-> Options…-> tab Mail Format-> button Signatures…
- Outlook 2010
File-> Options-> Mail-> button Signatures…
- Outlook 2007 and previous
- Double click on the txt-file of your signature to open it in Notepad (default).
- Edit your text and save it.
When you now reply to a Plain Text message, the modified signature will be added.
Note: If you are already replying in HTML format and your picture still doesn’t show up, clearing your Outlook’s Temp Folder might solve this.