Add picture to files

I am designing a members only website. I sell hosting, autoresponder services, websites and others. The members will be my customers. I am offering them a Customers Resource Area full of ebooks, graphic packs, templates, videos and more, so they have tools to get their businesses to a higher level, and be able to do a lot of things by themselves if they choose too.

Instead of installing a membership script and/or a download script, I am trying to make Dolphin Boonex work for me. Right now I am in the stage of figuring out how to upload those files, ebooks, videos, graphic packs, which I believe I can do just using the FILE function Module that comes with Boonex.

I began to try it, but for example, when I downloaded a PDF file, I want that when my members are browsing through the resources uploaded available to them, a picture is shown for that file. For example, when I upload an ebook on pdf format, and I have an image of the cover of the ebook, I would like to be able to upload it also and associate that image with the ebook, or graphic pack, or video, etc. so when members are looking for something, they do not only see the file name and description, but also an image of the resource.

Right now, when I upload a pdf file, the system automatically shows a pdf logo image associated to that file. So the space to do it is there, we just have to find the way of the system allowing me to choose what image to choose.

I do not know if the system can do this, if there is a module that can help me do this, or if this is something that has to be customized for me.

Any suggestions?