So instead of Halflings we have Skaven - rodent-featured anthropomorphic humanoids with aspects of rats, mice, gerbils, hamsters, squirrels, etc.
Rodents (and therefore Skaven) have long and constantly growing incisors, so Skaven like to have something to gnaw on, like a stick or a corncob.
Skaven are matriarchal and polyandrous - one female typically has several to a bunch of males exclusive to her. This has several possible repercussions on the culture, such as younger females ending up as adventurers because their matriarchs saw them as threats and pushed them out, or skaven males automatically deferring to a female of any race, or skaven females assuming that males of other races will defer to them, or whatever. Just an idea to play around with.
The Mouse Guard comics by David Petersen are a good touchstone, especially for Skaven with the (3.5E) Scout class. Note that Mouse Guard are mouse-sized and Skaven are ~hobbit-sized, but lots of the ideas transfer just fine.
Skaven class options are OD&D Halfling, 1E Illusionist, 2E Dark Sun Trader, 3.5E Scout, or 4E Warden with some specific options.
Skaven society is sort-of like hobbits in that they are agricultural (in fact they are the only race in Iron Canyons that grows very much above ground), they tend to prefer comfort and home over mystery and adventure (PCs may differ of course), and they tend to think a nice cup of tea or pint of cider will solve most problems that most people might be encountering.
Skaven are mostly vegetarian but will eat prettymuch whatever without being too picky. Most skaven cuisine is along the salads, stir-fries, veggie curries, nuts, fruits, beans, and corn line of thinking.
Skaven weapons tend to be kinda agriculturally-derived, like flails, bill hooks, machetes, sickles, scythes, hatchets, slings, and shortbows. Mostly light armors but a lot of skaven have scavenged armors with bits of metal plate or chain or whatever.
Most skaven are naturally helpful and good-natured, but they can be fierce in defense of what they love. Skaven homes are dug into the sides of hills like hobbit holes or in near-surface cave systems or in old elvish ruins or sewers. Many non-PC skaven are surface farmers growing corn, beans, and vegetables. Others are itinerant traders, with usually one female and her male attendants travelling together from place to place moving goods and scavenging ruins for anything of value to sell.
Skaven love pranks and illusions (1E illusionist class is an option; their primary spellcaster class). They love stories and especially tall tales but don't really have much that any of the other races would call 'religion'. That said, some skaven that live among dwarves have adopted the dwarvish religion, but its not a really good fit for them.
Skaven love to race (can go on all fours if not holding anything for faster movement), climb (racial bonus), swim (racial bonus), drink (no racial bonus), rut (no racial bonus, but 'multiplying like Skaven' is a common saying in Dwarven) and party for just about any occasion. Most prefer to be up at night and asleep during the day.
They love shiny treasures like amulets, bracelets, anklets, tail rings, gems, and baubles.
Skaven like to solve problems by common sense, hard work, ingenuity, trickery, or stealth. Violence is not preferred but sometimes its the only real option.
Skaven have a strong guest/host hospitality protocol.
Skaven are naturally immune to most plant and creature based poisons. Chemical and magic poisons still affect them and a number of such poisons were specifically developed by the elves for this purpose.
Skaven are often found as vassals/tenant farmers in dwarf-controlled country, with the skavens growing the aboveground crops and the dwarves providing the protection. Such is the case on the frontier of the Iron Canyons.
There are probably some Dark Skaven somewhere corrupted by elf magics, but they're not available as PCs. Probably hanging out deeper underground.
Occasionally a skaven or a whole group of skaven will get Rabies and go a bit crazy - thats bad news for everyone involved