I think the puddle and the number 6 could be examined more closely. Around the puddle I would look for carvings. It might be natural from water falling and wearing a hole..on the other hand it seems to be an odd and very particular shape.
On creek pic 6, you may have a greyish artificially modified rock wedged in the crevice..looks like it has an ear or two. The circled figure caught my eye because of the triangular like hat it has on..though it is not a pure triangle, I think it is notched at the top. Possibly, this is a turtle head given the context you mentioned.
Not a lot of streams around here, so no comment on the lines in the bed. Except..what i do is when i am suspicious, is walk around and find some natural cleavage or forms..that might be similar..as a reality check.
So, to me, it all looks worth a closer look but not enough yet to say one way or another if it is modified or not.