In this particular case I think you won't have any problem.
On the other hand on Imgur you can upload different photos... so if we are talking about links - we have to consider it not only basing on kind of website but also on content. In general - yes, it is possible to get a ban for sending a link in game, but only in case when content of the link contains content which is against Tibia Rules.
https://www.tibia.com/support/?subtopic=tibiarules
Your links can not contain:
- advertisements of products not related with Tibia,
- advertisements of selling Tibia Coins for real money,
- advertisements of selling your character for real money,
- screenshots shows that you use unofficial software,
- screenshots/info presenting how to abuse game bugs,
- supporting rule violation,
- information that you're a member of cipsoft (very often hackers used to write as CMs),
- hacklinks,
- false information about Cipsoft,
- inappropriate content - drugs, racist or sexual related,
- violating law.
The last point may be understood in many different ways, because against the law is for example:
- sharing someone's personal data without permission - not only Facebook profile, but address, private photos, phone number etc.
- advertising false passports (to be honest I haven't seen it via Tibian chat, but it is quite common that bots makes some advertisements on different Fansite's forums, so maybe it happens also in Tibia)