|Pic credit: Zigzag Journeys to Northern Lands; via Project Gutenberg.|
1- what about tieflings and other d&d playable races (halfeling, ferals, etc.)2 - what would be your choice for a typical d&d cleric ?1.) Tieflings could simply be any old human figure painted red or some other exotic color, maybe with some horns made from Milliput or Kneadatite. If you're looking for something more overtly devilish, there are certainly possibilities. I've discussed some devilish conversions I made previously. You may also want to check out these demon figures from Twilight Creations; they're a pretty good match for 1/72 figures.
I could do a pretty detailed post about halfings, but I'll keep it short (heh). Turns out there are a lot of DnD halfling figures that work with 1/72 scale. I'd also consider 15mm figures, such as these guys, for 1/72 halflings. Lord of the Rings hobbit minis from Games Workshop may also be something to consider; they look a little too chunky next to 1/72 figures, but aren't bad.
|A DnD halfling, Games Workshop hobbit, and Sven.|
I'm not sure what you mean by "ferals." If you mean wildmen, there are lots of 1/72 barbarian sets available (these are my favorite). If you mean beastmen, there are various 20mm and 15mm metal figures that ought to work, and headswaps with animal figures are always an option.
2.) There are two images that come to mind when one thinks of a DnD cleric; the armored warpriest, and enrobed holy man. For the former, any old knight figure (such as these) should do the trick. You may also find this post helpful for finding suitable clerics of this type.
There are more 1/72 scale guys in robes than you might imagine. For Christian priests, consider these sets among many. For more generic dudes in robes, these sets may be useful.
Any more questions? Feel free to ask the Cheap Fantasy Miniaturist, and I'll do what I can.