I am running a stored process - the code is located on a Unix server. It uses a proc report to display the output in Excel. I have most of the output format aligned correctly but the image does not show up in Excel. It shows "X" in red color.
My code is here. The ellipse is just to hide client information.
A red 'X' generally means that the image cannot be found. That means the location of your PREIMAGE tag must somehow be wrong when Excel opens the file. This Tech Support note: http://support.sas.com/kb/34/138.html
explains that "3.A physical path on disk is the least reliable method for referencing an image file in stored process output. Although this method might work in some circumstances, the path might not be accessible from other systems and client applications."
I suspect this is what you are running into.
There are a few things that I am uncertain about. You say this is in a stored process -- but Excel can receive 3 different types of output from a stored process:
ODS HTML (or HTML-based output)
ODS CSV (or CSV-based output)
SASReport XML (or XML-based output -- and this is not the same as TAGSETS.EXCELXP)
I do not know whether SASReport XML (for example) would even use the PREIMAGE tag specified in a TITLE statement. So partly, the answer to your question is going to depend a lot on how and where (what client app) you are using to execute your stored process. (whether directly in Excel with the Add-in, whether you have changed the &_ODSDEST macro variable in an override or whether you are using the Stored Process Web App).
Tech Support is probably your best resource for this question.