Funny thing but I noticed that everyone who posted here has a signature for an ICO in their signature place, so ... why so much pessimism? Are you or are you not participating in bounties and making cash out of it? Or you wear signatures just for fun?
Well now that you're asking the obvious, but maybe not, I can tell you that many coin projects reward users who participate in promoting their coin. It may the type of 'signature campaign' that you are thinking of so there is more than one reason to wear a project's signature.
For example, a couple of the projects I'm participating in reward for following, liking, RT/share, and adding a good quality comment (50 chars min.) on a FB or Twitter post that perhaps a more senior member already posted (senior not meaning the BCT rank, but involved for a longer period of time or part of the dev/mod group of said coin). In that manner you are also bolstering their likes, etc., and not necessarily your own. You may be asked to post your own Tweets, FB posts too, or write articles and post on Reddit, Steemit, or any number of platforms where the coin is established and then link to that article in the coins local forum as proof. You will always need to provide proof of participation and it will be checked for verification;this is how it really works most of the time... simple tasks but can be time consuming.
PLUS there is a requirement, normally, that you not only have an account on all of those social media accounts, but here on Bitcointalk.org too!So you wanted to know, and have received several answers regarding the amount of $$ per month not being a standard sum you can rely on but say, it may be anywhere from 10-500 coins per week, or 40-2000 per month. Now since they are all worth various amounts, or nothing at all, this is where the interpretation of how much money are you making breaks down. Those coin/tokens (as stated in this paragraph) can be anywhere from $.005-$15.00 each, depending on the market. YES, one of the projects was up at over $15, like $18 each but at that point all were waiting for it to go higher and were hodling; as long as the coins were being earned. Same project is now worth $0.80 a coin, ouch!
Bottom line is that if you want to participate in a way that you earn $$ then it can be called earnings from their bounty fund, which includes all types of promotion incl. the signatures here, which sometimes are optional but most of the time they are required. You only earn as a direct result of the signature at the bottom of your profile here if you are required, or earn, by posting on BCT since that is how more people will get exposure to the coin project by seeing the signature. At the same time, much of that is posting on the ANN of the same coin, go figure.
If rewards are distributed once a week, or every 2 weeks, the site is crawled to check that you've posted the min. required times per interval and that the signature is present. This can be done using bots. You can also look at it as being necessary to wear the signature for any involvement where you are rewarded by said coin project, regardless of the other promo tasks -- you may get nothing and disqualified for any particular reward round if you do not have the signature present; although
most rewards come for doing the other tasks in conjunction with wearing the signature to represent the project.
BTW I see you are doing mainly referral marketing via @CryptosPlanet and
https://cryptoplanet.club/, in addition to what it says about designing, etc., but you have not answered the question yourself yet?