- Flagging is the wrong approach
- Blend-Exchange isn't "adverting"
- Blend-Exchange is just suggesting use of these images
- It really doesn't constitute irrelevant adverting spam
- If they are a problem editing is the correct approach
Flagging is the wrong approach
Firstly I'd like to say that posts shouldn't be marked as spam just because they contain something that could be considered advertising. Spam is when a post is solely trying to sell something, and not contributing to the knowledge base the stack exchange is trying to build.
In this case, some of the posts with the image have been well received and gotten several upvotes, a sign that with the Blend-Exchange name and all they are still valuable and not at all spam. Flagging is out of the question, now to whether the image are spam is a different matter...
Not quite spam
Spam on stack exchange usually consists of people trying to sell garbage that nobody wants... Blend-Exchange is a charitable service, built out of volunteer hours and operating at a net loss of 100% with no income and operating expenses. In other similar cases these were companies, and the links helped them sell products. On the other hand, charitable organizations can spam for donations, but then again they are trying to collect money. Blend-Exchange doesn't collect money at all on its site. Blend-Exchange has nothing to gain other then increased taxing of its services, as well as a reinforced brand, but what does that brand even help?
Blend-Exchange isn't spamming, users are
Finally, normal users are spreading this accused spam by using the suggested embed code... Blend-Exchange isn't adding it to posts. One could claim that by giving out a blender guru tutorial link, or even by putting the name in this post that they are spamming. The only reason that Blend-Exchange cause an upset is that the image was fairly large and very orange. A better question may have been is it incorrect to put attention grabbing content? Is the subtlety of the brand's name important. The point is mentioning a service isn't necessarily spamming, the line can be fine, yes, but I don't think this crosses it.
Do edit if all else fails
How to handle the images, amusing it is spam, which it is not: Editing the posts.... flagging isn't appropriate, since the moderators will simply have to edit it since it on its own doesn't justify removing the post, see first paragraph.
Special note from the admin of Blend-Exchange
This is a Community Project
As the manager of the project, I'm open to suggestions from the community. (I also have to say no from time to time in the best interest of the project, I promise to be nicer about it then Linus Torvalds though :P ) Even though Blend-Exchange is under no obligation to change the images, a change will occur as a result of this.
I appreciate your support of the project, even if its unconventional... I hope this doesn't affect your view of the service, Its trying to solve a problem, not create one.
PS Blend-Exchange is under no obligation to act upon this much like any other file hosting service wouldn't be liable for its embed code... however since this community is central to its operation as said above, Blend-Exchange will be changing as a result.