Given that mobile headers are very personal and unlike icons are one per blog, you should help me make it really YOURS, which means you'll have to tell me who your character is, if you want text on it, type of background...
Basically anything that you don't want me to do on a whim has to be specified by you. If you don't care about the position your character will be in, I'll pick. If you care, tell me. And same goes for everything else. Could help to give me their tag in your blog so I can see what aesthetic you like.
You could give me the images you want for your character and/or any other image to be thrown in, or a link to a video to make a gif you want.
Standard size is 640x360 on tumblr, but you are free to ask for a different size, if you want to use it for your pinned post.
Changes to the final product:
You commission me > I make the header > I send you a badly taken photo with my phone so you know it's real > you pay > I send it to you via email or wherever > you can request me to edit it twice, each time I'll send it back to you and you can tell me if it's okay. By the third time you'll have to pay me half of the price of the header for each new change and back and forth we do. This is also why it's more convenient if we discuss what you want before.
How long will it take? Depends on how complex it is and how hard it was to find resources if you didn't have anything to give me, especially if I had to download videos to make gifs.
Feel free to use my examples on this page not only to know what to ask for, but also to say like 'I want this thing in that shape/position like you did for that header over there'.
Each type of header has its specific price, but here are some general information that are the same for whatever you are asking me to make, headers or not:
-if you want to have 2 choices I can make you two with variations like "this is the header with a light background and this is the one with a dark background" or something we'll agree on, and instead of making you pay for two separate headers, you'll pay fully for the first but the second one will have a 30% discount. So if you ask for two with gifs and overlays instead of paying a total of 20 you'll pay 17 euros.
You can pay me via paypal.me
Price: 5 euros.
Price: 6 euros if it's just one static image with one overlay like in the first example, 7 if I make the background too like in the second example. 2 extra euros for each overlay after the first I add. So the third example here, having my own background (7 euros) and 2 overlays (+1) would cost 8.
Example 1 (static + overlay), 8 euros
example 2: my background + one or more overlays: 8 euros
Price: 10 euros.
Additional 3 euros for each gif or overlay added other than the first gif and first overlay.
examples of static background and a gif used on top of an overlay figure (and text in the first two):
Example of two static images with an overlay and a gif
two different overlays over separate static images