Those are great pictures, but there is only one spinal cord segment there.
What I mean is given a cross section of an actual spinal cord, is there any easy way to remember (or whatever) what level of the cord that segment is? For example one easy rule- is there a lateral horn? Yes- then it is T1-L2.
Cervical spine - Oval lots of white matter
Thoracic - Round and lateral horns like you said
Lumbar - Round and big ventral horns with lots of gray matter
Sacral - Round and even more gray matter
You can always use the presence of nucleus gracilis and/or cuneatus to help determine where you're at as well.