I love the mods so far! Keep em coming! (Both the Campus Bookstore and Butcher Shop were made by me, nice to see what y'all are doing with them
I wanted to clarify some of the texture usage for you so you'd be better able to make the buildings look as you want. Each building has 4 or 5 textures associated with it- diffuse (color), bump (technically it is surface normals, but the naming convention calls them bump), specular (shininess), emissive (glow), and ambient occlusion (shadows). Typically you will want to leave the amb_occl alone, as it operates slightly differently from the others, but changing the others can have dramatic effects on the buildings' appearance.
The changes to the diffuse are the easiest and most apparent to make, this is where you will add all color info including logos, new paintjobs, etc. The bump probably has the most impact after the diffuse, but it can be finicky to play with. The proper way to make a bump map is to run the Nvidia normal map filter (plugin available for free for use with Photoshop, I can't speak to other paint packages) on a grayscale image (we typically use a scale of 12 in that plugin). You can tweak the existing maps though, as long as you only use the colors found within the existing bump map- this is kinda
asking for trouble, but as long as you are careful it should be ok to do. By careful, I mean not attempting to add much detail; you'll probably have better luck taking detail out
, like the signage at the top of the butcher shop, or the hands and numbers on the clock face of the campus bookstore.
The spec map affects the shininess of the texture, with lighter areas appearing shinier, and black areas as non-reflective. Colors can make the material appear more metallic. If the building has a lot of glass on it, chances are it has the Glass shader applied to it, in which case the alpha channel of the spec map will affect how much sky is reflected in glass areas (it's easy to blow this way out, so keep changes subtle for best effect).
The emissive map controls areas which light up at night (or when the ambient light falls below a certain threshold). Areas which do not light up should be black, and you can play with the effects of lightening, darkening, or colorizing parts of the map. For windows with items inside (such as the butcher shop) it is often good to have a modified version of the diffuse map (the meats in the window, for example) be also present in the emissive.
Hope this helps! Keep up the good work!