Shadowcall should be Greater, not Lesser. It grants at will casting of a WIDE variety of 3rd-level spells as early as 6th level (only 1 level after Wizards get 3rd level spells). It's far too versatile for such a low end invocation. The open-ended nature of Shadow Conjuration also means that you'll have access to spells that function very differently when removed from the daily limit of spell slots.
On a related note, Bright Shadowcall should mimic Greater Shadow Conjuration (6th), not Shades (8th). I'm also on the fence about Bright Shadowblast mimicking Greater Shadow Evocation (7th, Evocation).
Edit: An alternative, if you want to keep the Shadow Conjuration concept as early as Lesser invocations, is just to limit the spell level copied. 1st level and lower should be fine. You could probably push it to 2nd if you wanted.
