As you might know, Minecraft data enters FME as a point cloud. Probably the best way to start is to divide the data by block type. Use the PointCloudSplitter to do this. You need to split by BlockID. If you've built a building using stone, then keep that ID, like so:
You can find a list of block ID numbers in many places online, including here. In the above, 1 is the stone walls, 5 is the wooden floor/roof, 20 are glass windows, etc.
Notice I'm choosing not to keep IDs 2 (grass), 3 (dirt) and 7 (bedrock) since they aren't part of the building I want to work with. Of course, for a 2D map I probably would keep them.
What might I do next? Well, it depends what you want. In this workspace...
I turn the point cloud into point features (PointCloudCoercer), get the x,y,z coordinates of that point, then use VertexCreators to turn that point into a 1-unit square polygon.
If I want that to be a 2D map, then I could just flatten it out (with a 2DForcer) and merge adjoining polygons together with the same ID. Of course, you need to decide which block type wins out, where there are multiple blocks stacked up on each other.
One way you could do that is to pick the highest block (highest z). Use a Sorter to sort by z and then a DuplicateRemover to remove duplicate x and y values. There are other ways, but they would depend on what you exact rules are.
Alternatively, here I extrude the blocks into 3D. That way I end up with a vector model that is made up of blocks, just like in Minecraft:
I could then add textures or appearances to give it a more polished look.
I hope this helps. If you need more assistance then please do post, either here or on the FME Community Answers site (fmepedia.safe.com)