My suggestions, segments with open sections for a door, single and double width, and also segment with a hole for windows sections, of different sizes. ramp segment, both as a wedge triangle, and the plank type ramp, though it will have to be watched how its built as these can be slotted together to form longer ramps, floor segment of a flat brush, ie no Y depth, also as angled version for ramps. Segment of 100x100x100 units, these are usefull for using, in the same way minecrafts blocks are usefull, you could also make varieties of these, same Y depth of 100, but smaller in X and Z, as I dont know the size in the texture I cant say the size, as the smaller blocks must conform to it of course. A wall of half the height, not the usual 100 units heigh, also sections to put on the end of these, 45* slope on them, so 50x50x50, 45* cut, you may want a version of these for the full height walls. Wall segments of different thickness, as I dont know the texture grid sizes I cant say the exact thickness, it will depend on what size the texture is to conform to the grid you have textured. I have other ideas, I may have to draw them to illustrate.
