Flyer / poster templates
Yes. Quite a few people have one exclusive account and one non-exclusive account. You can even have two exclusive accounts if you want, to focus on certain items, but keep in mind that it will take you twice as long for your commission to increase than having just the one account.
I’ve not heard of any limit on the number of accounts you can have, but questions might be asked if you’re into double figures!
I can understand wanting two accounts if you’re selling music on one and flyers on the other… but if you’re saying you want one for flyers and one for posters, there’s probably not much point.