These races are either not a major part of Escarnum's core and history, or are not included in the setting by default. However, they can easily be included in your campaign if you desire. If the group does not wish to add new races, this section also provides suggestions for replacing the desired race with an equivalent race from Escarnum's core.
Races which are not mentioned here can still have a place in Escarnum. Whilst Alm itself is fairly well-established, its neighbouring continents are largely unexplored, and even within it, wild places such as Kaath and the Barrens could easily provide new races a place to develop. Other races might be unique occurrences – magical experimentation with creatures was a common practice in the history of the Overseers, and there is the possibility that they might have created many other magically-altered hybrids and offshoots of the existent races.
Dragonborn evoke the importance and majesty of perhaps the most iconic creature in common fantasy. In Escarnum, however, dragons are not nearly as prominent as in most Dungeons & Dragons settings; they are far more rare and less integral to the world. Between the scarcity of dragons and the absence of a creator-god such as Bahamut, it's no surprise that dragonborn are not a PC race in Alm.
If the dragonborn did appear in Alm, they would most certainly spring from a natural source, rather than the hand of a deity. Since dragons are rare, perhaps dragonborn originated in a time long ago, when their ancestors were more plentiful; perhaps something happened in that era to wipe out many of the dragons, giving the beast-kin their chance to seize control. On the other hand, perhaps dragonborn never dwelt in Alm, and instead hail from one of the less-explored continents. Maybe they are more like equitarn, hybrids created by the Overseers from human and dragon traits.
Alternatively, there are plenty of substitutes for the dragonborn in Escarnum; gnolls mirror their offensive strength, while equitarn and jotunar provide the same hardiness. Soratami and stoneborn also share a dragonborn's dutiful, regimented nature.
Dwarves are a race which is not included in Escarnum by default. Essentially, the common roles of dwarves as a race – those of miners and/or craftspeople – is filled by the kobold clans. If the group wishes to include dwarves in setting, a good place for them may be as allies of the kobold clans, working side-by-side in the mountains; alternatively, they may be a race that rivals the felbraug for age, who faintly remember some of the precursors' secrets that now exist only in the ruins of Aethys and the relics below ground.
If the group does not want to add dwarves to the setting, a kobold of the Vaess clan may serve well in the role of a technologist or item-crafter. Alternatively, if the desired aspect is that of a sturdy, unrelenting warrior, an equitarn or gnoll should be a more suitable replacement.
Gnomes are not included in Escarnum by default. The appropriate replacement will depend on the role they are to play; some settings see them as tricksters, others as bumbling inventors, others as bardic tale-weavers, others as eccentric wizards. Indeed, the somewhat ill-defined identity of the gnomish race is a major reason for their absence from Escarnum's world. In Escarnum, most of the gnome race's various roles are filled by the various clans of kobold, especially that of inventors. Alternatives include felbraug, for magic-using gnomes – a felbraug's psychic nature and small stature make it a good replacement. For bardic or trickster gnomes, the abilen is a substitute – they possess the same social grace and small size.
Halflings are not included in Escarnum by default. In most settings, halflings are smaller and weaker than medium-sized races, yet known for their agility and social natures. In most cases, an abilen is the ideal replacement for a character who would be a halfling. Alternatively, both kobolds and felbraug match the small stature and nimble nature of the halflings, and can make excellent substitutes for the favoured halfling rogue.
Former humans influenced by a fiendish taint, tieflings are the evidence of mortals consorting with evil extraplanar powers. There is no reason that such a thing could not happen in Escarnum; mortals still seek power from sources outside their world, and evil entities of all sorts still seek to corrupt and control mortals and their affairs. In fact, many demons and devils are particularly eager to exert their influence on the material plane, in hopes that they will eventually attract a cult following.
However, the planes of Escarnum are more abstract than those of other settings, and their borders more difficult to cross; a creature like a tiefling would be all but unique amongst the "ordinary" races. Most likely, a tiefling would not be born, but would be "created" by an infernal creature seeking to empower one of its followers – or the unfortunate child of such a follower.