I want to publish a very meticulously designed Sketch kit on GitHub. Though, I wish anyone who would use it in their open/closed source projects to be obligated to have my company's title mentioned somewhere in the designs.
Which license would fit?
Your wish is problematic in several ways.
There are licenses with a similar requirement (such as the 4-clause BSD license, which requires that you mention the licensed product/library in all advertising material), but these licenses are considered problematic by the open-source community:
This clause was objected to on the grounds that as people changed the license to reflect their name or organization it led to escalating advertising requirements when programs were combined together in a software distribution: every occurrence of the license with a different name required a separate acknowledgment. In arguing against it, Richard Stallman has stated that he counted 75 such acknowledgments in a 1997 version of NetBSD. In addition, the clause presented a legal problem for those wishing to publish BSD-licensed software which relies upon separate programs using the GNU GPL: the advertising clause is incompatible with the GPL, which does not allow the addition of restrictions beyond those it already imposes -- Wikipedia
I would expect that the artists using your Sketch pad would object violently to such a requirement, as it would probably be considered a defacement of their artwork.
The content you create using a program is not constrained by the copyright license of that program, unless the output actually contains portions of the program that are eligible for copyright protection. In the large majority of programs, that is not the case.
This means that whatever you state in the copyright license of the Sketch pad, this has no effect on the license of the artwork created using the Sketch pad. As a consequence, if someone did follow your wish, you can't require that the attribution stays in the artwork.