Good lifegain! I noticed that this deck is lacking win conditions; the only ones that really punch through for damage are the ajani's pridemates. Archangel of Thune can boost all of your smaller creatures into larger ones. If you go green, Ageless Entity will work very well too. Some spot removal, like Path to Exile, Oblivion Ring, or Journey to Nowhere could help too. Mistveil Plains is a land that gives you life, as is Radiant Fountain. Instead of pulse of the fields, why not try Survival Cache? It'll give you the same amount of life, and because the point of this deck is to have more life than your opponent, it will net you two cards as well. Decks that play there hand quickly, like this one, often benifit from card draw. I can't think of an alternative to life burst in mono white, but in white-green, Heros Reunion should do the trick. As far as adding green is concerned, Sunpetal Grove, Stirring Wildwood and Razorverge Thicket are all relatively inexpensive dual lands that can give you mana fixing.

I really like Survival Cache, good call! I was really tempted to put in Archangel of Thune or Felidar Sovereign, but decided that I didn't really want to make a deck to win, but to annoy my opponent by just sitting there and healing. I did decide to splash in some green too.

Hmm . . . Soul's Attendant Soul Warden Essence Warden Martyr of Sands Serra Ascendant. At worst, the Ascendant should help you wall a big creature while gaining you extra life.

Feed the Clan instead of Rest for the Weary and Wall of Reverence instead of Nyx-Fleece Ram maybe?

I've got a selesnya life gain deck if you wanted to check it out, The Exponential Wurm Of Life

I like the consistency of Nyx-Fleece Ram for helping with card draw when working with Well of Lost Dreams as well as his cheap cost. That said, I really really should pick up some Wall of Reverences for going up against a deck with lots of flying...

Love the voracious wurm in your deck, you can get crazy amounts of life in a turn with the rhox faithmender in play!

Also, I really really would like to put Serra Ascendant in this deck, but she's too rich for my blood. Maybe wizards will reprint her sometime soon...

+1 for Lich's Mirror.

Just a few annoying annoying white cars I can think of: Worship, Pariah, Wall of Essence, Perimeter Captain. IMO Perimeter Captain would make a good replacement for Pride Guardian as it has one more point in toughness and the abilities can stack. Pariah could just enchant a Wall of Essence and heal from the damage that would of killed you, considering it was combat damage you would have taken and Worship because of reasons.

Oh hoh, I'm liking perimeter captain... Thanks!

I would recommend running a couple copies of Melira in the sideboard...infect doesn't care about how much life you gain.

May I suggest an Alhammarret's Archive?

Great suggestions both, thank you!

Another suggestions...with the X, gain X life creature, how about Nykthos, Shrine to Nyx?

All of your permanents have white mana symbols in them, so you could wind up with massive life gain...and if you don't have that guy it, it will still provide you with a bit of ramp to gain life faster! It also plays nicely with the Well of Lost Dreams.

I'm also going to recommend Sun Droplet over the spell-bomb as multiple copies can gain you an insane amount of life, especially vs burn.

Oh yeah, I've actually got an extra Nykthos too, may as well drop it in!

Sun Droplet I keep going back and forth over. It's a good card for regular lifegain, but not quite as consistent as Nyx-Fleece Ram. It's also a good low cost artifact, but without the card draw flexibility given by Sunbeam Spellbomb. I might try to find a combo with it to make it work...