I'm trying to create something close to the sample application with some other products. I have a table with BLOB column for the products jpg files. However, I have encountered the following challenge: the preview is not working.
Well that explains the problem. The url NEEDS to be a viable url to an image -- a procedure needs to be called to (in essence) spit out the blob to a mime-type of jpeg so the browser can display it. Although there are several ways to achieve this -- since you basically see it "working in one place but not another", take a look at how the working image's URL is generated on the page where it's working.. APEX offers an item type that can display an image, but you can also use PLSQL code to insert such in the rendered output anywhere. If none of this helps, there are many hits via google that discuss all of this in the detail you'll need.