I found another issue related to support for resource_name. While it works fine for to_representation when my resource has many related resources, i.e.

"relationships": {
 "portal-images": {
 "meta": {
 "count": 2
 },
 "data": [
 {
 "type": "ownerportal-image",
 (...)

(here, i could return ownerportal-image instead of portal-image successfully)
it doesn't work when the relationship is the other way around, i.e. my resource is related to only one other resource:

"relationships": {
 "image": {
 "data": {
 "type": "image",

(here, i would have expected ownerimage instead of image)

After debugging a bit, i found that the problem is related to (relations.py, 140)

resource_type = None
root = getattr(self.parent, 'parent', self.parent)
field_name = self.field_name if self.field_name else self.parent.field_name
if getattr(root, 'included_serializers', None) is not None:

In the successful case, self.parent refers to a ManyRelatedField, and self.parent.parent to my serializer.
In the unsuccessful case, self.parent refers to my serializer, while self.parent.parent is Null.

For me, changing the initialization of root to

root = getattr(self.parent, 'parent', self.parent) or self.parent

fixes the problem.

Since i'm a bit unsure if my fix is the right way to go, i thought i'd post this as an issue first to get your feedback. Thanks in advance!