Grammar question: Past participles used as adjectives?

I have a doubt about the usage of past participles when used as adjectives. For instance:

1. The image shown on the home page is wrong.
2. When don’t get the expected thing, I usually get angry.
3. And suddenly, they saw a series of confounded Ferris wheels moving towards nothing.

In above examples, “shown”, “expected”, and “confounded” are being used as adjectives. What do you call such verbs? I know these sentences can be constructed in other way.

For instance:
1a. The image that appears on the home page is wrong.
1b. The image appearing on the home page is wrong.
?1c. The image showed on the home page is wrong.

>> I put a question mark before “1c”. I think idiomatically, it’s not correct.

Please help me out!