You can add a title to the plot, set the figure width and height, change title font, etc. Below is a summary of properties which can be added to change the style of the plot:

import pandas
from bokeh.plotting import figure, output_file, show
 
p=figure(plot_width=500,plot_height=400, tools='pan',logo=None)
 
p.title.text="Cool Data"
p.title.text_color="Gray"
p.title.text_font="times"
p.title.text_font_style="bold"
p.xaxis.minor_tick_line_color=None
p.yaxis.minor_tick_line_color=None
p.xaxis.axis_label="Date"
p.yaxis.axis_label="Intensity"    
 
p.line([1,2,3],[4,5,6])
output_file("graph.html")
show(p)