No, they should be visible to you and everyone else. if you attach a file using the "manage attachments" tool the images will appear as thumbnails at the end of the post. If you click on a thumbnail, it will open the file in a viewer, not in a new window. Click the picture in the viewer and it will open the file in a new window (this also works if there is an image you are trying to view but won't seem to load...if you click on the black part where the image would be, it will immediately open it in a new window).
Just play around with it, or check out some threads in the Support forum that address uploading images.