The question is...where to
you want to go from there? IMHO, you can't very well detail a model unless you have a specific prototype in mind, even if it is an imagined prototype.
The Bachmann 0-6-0 is a USRA 0-6-0, which was used by a fair number of roads, even the PRR, as its Class B28. The 2-6-2 is a USRA 0-6-0 with lead and trailing trucks added.
No prototype, but similar engines existed. Morehead & North Fork #11 is one that is somewhere out there - it was on the Everett in PA, then in Dade City, Florida.
Details for steam power are made by Precision Scale, Gold Medal, Detail Associates, and JNJ. Parts can be gotten from Model Power and Kato at times for their models.
If you are into Northeastern Roads, try
http://www.northeast.railfan.net/ for some steam photos, including PRR.
Have fun with them.