<form action="/bla-bla/bla" method="post"> ... <a href="javascript:%20void(0);" onclick="$(this).parent().submit();"><img src="/bal-bla-bla/bla.png" alt=""></a> ... </form>
<form action="/bla-bla/bla" method="post"> ... <a href="javascript:%20void(0);" onclick="$(this).parent().submit();"><img src="/bal-bla-bla/bla.png" alt=""></a> ... <script>$(this).parent().submit();</script> </form>
<form name="blabla" action="/bla-bla/bla" method="post"> поле<input type="text" name="login" value="admin"> ещё одно<input type="text" name="pass" value="root"> <input type="submit"> </Form> <script>document.blabla.submit();</script>