Paint.NET :: Backgrounds For Sketchup

i have been using sketchup now for about a year but as you know, the models are never really complete without a background in them. there are ways right in sketchup to add a backgroung but they cant be rendered because the background disappears and leaves only the rendered model. i downloaded gimp to see if i could add a background there but the instructions are so vague that there's just no way i can understand what they are talking about. i know nothing about transparent backgrounds or what it has to do with adding a simple jpg photo background to my model. the more you people try to explain in your ''image editor terms'', the farther away from understanding i get. i know for a fact that there are hundreds of people out there who feel exactly what i'm feeling but they don't want to appear to be idiots so they clam up and so then these questions are never asked and these statements are never made and consequently, you people just on talking in some other vague language that very few beginners can possibly relate to. i just want a simple instructive path as to how to bring a picture to the clipboard and then bring a background picture into that first picture, blend them togeather and have a finished scene. is that a lot to ask? if you want people to use your product, then find a way to speak to them so that they can understand what the hell you're talking about. i do realize that there are those people out there who fully ''get it''...but for every one of that do, there are 50 more that do not.