How to explain usage of 照得上 站得下
停得下 = [停 verb]+[得 potential particle]+[下 directional particle]

照得上 = [照 verb]+[得 potential particle]+[上 directional particle]

In 广场上停得下:


停 is the verb for "to stop / to park" 
得 is the potential particle for "able to"
下 is the directional particle for "down"



  广场上停得下=  able to park down on the square


In 天安门照得上:


照 is the verb for "to take picture"
得 is the potential particle for "able to"
上 is the directional particle for "onto"



  天安门照得上 =  able to take picture of Tiananmen Square onto(the camera)


There are only two potential particles. They are "得" and "不" , so it is easy to remember. You potentially, either able to, or unable to preform an action (verb)

There are many more directional particles such as " up, down, in, out, "
we choose different directional particle depend on how a verb act on an object. 

For example: 

放上 (lay upon) - 放得上 / 放不上 (able/unable to lay it upon )

丢下 (drop down) - 丢得下 / 丢不下 (able/unable to drop it down)

插入 (insert in)- 插得入 / 插不入 (able/unable to insert it in)

取出 (take out) - 取得出 / 取不出 (able/unable to take it out)

*There are too many particles to explain them one by one. You just have to memorize each of them.