Uploading a group of similar textures - numbering in the title allowed?

You shouldn't use numbers, they are meaningless with millions of assets. Describe the difference as a text. The textures ought to be quite distinct among each other.

Ah, thank you guys! I was sure I have read somewhere that using the same title for multiple submissions was not allowed. But if it is, then everything is fine. 

There is no rule against using the same title in multiple submissions; however, as noted by @daniellei4510  you should strive to add more descriptive terms that will help Buyers narrow down the choices since there is already a lot of competition in this genre.

I don't think it would hurt to use the same exact title, but if there are at least noticable variations between each one--color variations for example--noting that in the title would be more descriptive than just a number.