Can ITNM run discoveries based on seed files and can the discoveries be based on a range of IP addresses? 

Seeding discovery
To seed the discovery, provide the starting points from which to look for devices.

Use the following methods to seed the discovery:

Ping finder

Seed the Ping finder with a device or subnet address at which the finder begins looking for devices. You can specify seeds for the Ping finder and save these seeds. You can separately decide whether to activate the Ping finder for the discovery.

File finder

Seed the File finder with a text file on the Network Manager host to which you have read access. This file must be a structured text file that contains the seeds in the form of IP addresses and device names in columns. You usually use a file that already exists on the Network Manager host. However, if you want to create a new file to hold the seeds, you need to have write permissions for the directory where you want to write the file.

Scoping discovery
To scope the discovery for IP-based devices and subnets, define the zones of the network (that is, subnet ranges) that you want to include in the discovery, and the zones that you want to exclude.

as per http://www.ibm.com/support/knowledgecenter/SSSHRK_4.2.0/itnm/ip/wip/disco/task/nmip_dsc_dscnwusinggui.html

Hello, please refer to the URL Zalan provided to understand more about seed file based discovery. Yes, you can discover devices using seed files, but ITNM doesn't support ip ranges as either Scope or Seed, instead you can use Subnet based or wild cards (192.168.1.*) if it helps.

I would also advise you raise RFE @ https://www.ibm.com/developerworks/rfe/?BRAND_ID=90 if you could for the same request.

Hope that helps, let me know if you have other questions.

Krishna.