First you need Okeanos tools
CXLPackager.exe -- https://mega.co.nz/#!YNoEVabA!frOugj97k75e7mBTEgmTkerCOOGQs8L_GDJp9O-7Cws
I will use the "r_wy_road_05x40x40.sgbin" in this example.
Unpack it with cxlunpack,exe.
go to the folder where you extracted the files. rename them to something new. note: you cannot change the character count, but can change to any character..
at this point you would edit the diffuse, nmap or whatever texture you want using this method. http://forum.citiesxl.com/viewtopic.php?f=59&t=1375
next you would open the files graph.bin and r_wy_ohad_05x40x40 with a HEX editor.
The easiest and safest thing to do here is press Ctrl + F and search\replace any of the old names with the new ones, but use as much of the word as you can, as to not replace something else,
eg. search for "r_road_10x20" and replace with "r_ohad_10x20" this will update the new texture names.
next search for "r_wy_road" and replace with "r_wy_ohad".
the Graph.Bin has the name of the sgbin, so whatever you name it here, has to be the name of the new sgbin file as well.
pretty much any file that you renamed. and save\close them both.
Next open CXLPackager.exe and open the ORIGINAL sgbin, eg "r_wy_road_05x40x40.sgbin"
now right click on the files to be replaced, (all of them except the 0.0.00. and 255.255.) and choose replace,find the new ones.
once you've replaced them all, right click again and choose properties, and rename so they match the new filenames.
then file save as, the same name you put in the graph.bin, "r_wy_ohad_05x40x40.sgbin"