Can we customize test report in SOAPUI at the Project level

The different sub tabs gives you access to the underlying XML for main reports, sub reports and templates as well as project level report parameters. Project level items can be created, removed and edited as desired, while global items can not be modified inside soapUI. They have to be modified in the file system and reloaded with the Reload button in the top toolbar for changes to be applied (more on that later on).
2. Report Structure

soapUI structures reports as follows:

Main Reports are the top level templates which are shown in the Create Report dialog and visible in the Available Reports tab above. A Main Report template is a standard jasperReport template which receives the report-scope specific model item as its DataSource, for example when generating a LoadTest report the data object passed to the report is a WsdlLoadTest, whose properties can be defined as Jasper fields in the report and used as such.
Main reports can include any number of Subreports (shown in the Subreports tab) through the standard JasperReports subreport mechanism in combination with a soapUI-specific URL prefix ("subreport:"). A Subreport gets its data from the specified DataSource which is available when the report is being generated. Looking at the Subreports tab we can see all available subreports and their corresponding DataSource:

subreports-tab
For example, the MetricsReport subreport gets its data from ReportMetrics DataSource and is included in the all main reports with the following syntax:

1.y="98" width="535" height="30" isRemoveLineWhenBlank="true"> $P{IncludeResults} ... $P{TestSuiteMetrics} "subreport:MetricsReport"
As you can see the subreportExpression uses a soapUI-specific "subreport:" URL-syntax which soapUI uses to locate the specified SubReport template. The fields exposed by the TestSuiteMetrics DataSource are correspondingly defined in the MetricsReport template:
1.......
Templates allows for management of common blocks of template XML. The tab is as follows:

templates-tab

The above example template can then be inserted to any report with the familiar property expansion syntax:

template-example

Finally, Parameters allow for parameterization of report content without the need of recompiling the underlying template. The Parameters tab allows you to add parameter values as desired: