It is impossible to issue a blanket ruling based on a snapshot description of a hypothetical Robot design. Furthermore, please review the Q&A Usage Guidelines, specifically point 3, "Quote the applicable rule from the latest version of the manual in your question."
The rule in question is R10, quoted here for reference:
<R10> A limited amount of tape is allowed. Robots may use a small amount of tape when used for the following purposes:
a. For the sole purpose of securing any connection between the ends of two (2) VEX cables.
b. For labeling wires and motors.
c. For covering the back of License Plates (i.e. the “wrong color”).
d. For the purposes of preventing leaks on the threaded portions of pneumatic fittings. This is the only acceptable use of Teflon tape.
e. For securing and retaining a VEXnet Key 2.0 to the VEX ARM® Cortex®-based Microcontroller. Using tape in this manner is highly recommended to ensure a robust connection.
f. In any other application that would be considered a “non-functional decoration” per <R12>
As your description does not sound like it would fit into points "a" through "e", the question that a Head Referee/inspector would then ask themselves is whether the contact paper is a "non-functional decoration". R12 is partially quoted below:
<R12> Decorations are allowed. Teams may add non-functional decorations, provided that they do not affect Robot performance in any significant way or affect the outcome of the Match. These decorations must be in the spirit of the competition. Inspectors will have final say in what is considered “non-functional”. Unless otherwise specified below, non-functional decorations are governed by all standard Robot rules.
In order to be “non-functional,” any guards, decals, or other decorations must be backed by legal materials that provide the same functionality. For example, if your Robot has a giant decal that prevents Cubes from falling out of the Robot, the decal must be backed by VEX material that would also prevent the Cubes from falling out.
It is ultimately at the inspector's discretion whether or not a given decoration is affecting Robot performance. A decal which provides more (or less) grip than standard legal materials would likely be considered to be affecting Robot performance, and would not be legal.