The experience table in Frostgrave has basically been a source of discussion since the emergence of the game, and with a new campaign starting, our local group decided to adapt a new table partially based on the comments made by Joe on his blog and as they are found in several scenarios.
Overview used table:
+50 For each treasure recovered by the wizard or any member of their warband.
+20 For each randomly encountered creature killed by the wizard or any member of their warband. If the creature has a starting health of 14 or higher, instead gain +50 experience. If the creature has a starting health of 6 or lower, instead only gain +10 experience.
+20 For each different spell cast by the wizard or apprentice during this game.
+20 For each spell of the wizard’s own school of magic cast by the wizard or
apprentice on the natural roll of a 20.
+10 For each time the wizard or apprentice rolls a 1 when trying to cast a spell
from their own school. Best to learn from your mistakes.
For starters, we kept the 50xp for treasure, so that most people (typically leaving with at least 2 treasures) would gain a single level from that.
We then scrapped all the others, in their stead adding 20xp for each different spell cast by the wizard or apprentice during the game. This addition has several advantages over the normal 10xp per spell: it obviously encourages variation in casting, which makes for more interesting games. Interestingly, it also gives a good incentive to finally learn more spells from those many grimoires otherwise collecting dust in the corner of your home base. For a starting warband, it also caps xp from spells to 160 (8x20), meaning most wizards will level up 2-3 times after each game, but never much more than that.
To add a few more possibilities for gaining experience, another two magic-related rules were included: 20xp for each spell of your own school cast on the natural roll of a 20 and 10xp whenever you roll a 1 when trying to cast a spell from your own school (trial and error...). Both to give a slightly larger impact for your choice of starting school and to make it worthwhile to cast your 'own' spells more than once during the game. The first also means it doesn't feel like 'a waste of a good 20' when casting a regular (non-resistable) spell.
Finally, a single rule for kill xp - but the opposite of the normal version. 20xp for each randomly encountered creature killed by anybody in the warband; which is increased to 50xp if the creature has a starting health of 14 or higher, reduced to 10xp for a starting health of 4 (or lower). It felt right to reward people for learning about the inhabitants of the frozen city (by finding out how to kill them), and it means being ambushed by big critters isn't entirely horrible.
So far the reception has been very positive. Wizards can still be a target of attacks to shut them down, but there is much less incentive to all-out annihilate the enemy wizard or soldiers unless it's tactically sound at that moment. Perhaps related to the changes, a large variation in wizards is being played, some of which may not have been as popular under the normal rules. Progression has so far been gradual and similar, people typically gaining at least 200xp but less than 400xp per game. In other words, if you feel like giving some alternative rules a spin, I can certainly recommend something along these lines.