Consider replacing some of the monsters on the monster-summon list with other monsters utilizing equallent Level Adjustment templates. I created a 1st level Human Cleric with the Summoning domain and then poured through all my books looking for templates on par with what what the Planner Handbook and Manual of the Planes said were roughly equal power. I then applied those templates to the creatures (after using the base <non celestial or fiendish> profile). Created for some interesting but still fairly balenced creatures. I Only did it for 1st level good (I left a couple as celestial) monster summon list. I already applied the Augment Summoning template as well.
Spell Focus [Conj.], Augment Summoning, Summoner Domain bonus of +2 Caster Level on summoning spells makes for a rather impressive 1st level summoner (rem. Human Cleric).
if requested I can send the word file <gotta dig it out>.
BTW Sir Draconion, The Planner handbook has a small blurb about about alternate summoned monsters at (I belive) The back of the monsters section. As far as I Know, nothing really prevents you from swapping out one of the normal monster summon monsters for a different one (which was basically what I did).